In many growing tissues, slowly dividing stem cells give rise to rapidly proliferating progenitors that eventually exit the cell cycle and differentiate. Growth rates are limited by nutrient availability, but it is unclear which steps of the proliferation-differentiation programme are particularly sensitive to fuel supplies. We examined how nutrient deprivation (ND) affects stem and progenitor cells in the ciliary marginal zone (CMZ) of the amphibian retina, a well-characterised neurogenic niche. We show that ND specifically blocks the proliferation and differentiation of progenitor cells through an mTOR-mediated mechanism. By contrast, the identity and proliferation of retinal stem cells are insensitive to ND and mTOR inhibition. Re-feeding starved retinas in vitro rescues both proliferation and differentiation, and activation of mTOR is sufficient to stimulate differentiation even in ND retinas. These results suggest that an mTOR-mediated restriction point operates in vivo to couple nutrient abundance to the proliferation and differentiation programme in retinal progenitor cells.
Differentiation; mTOR; Nutrient deprivation; Proliferation; Restriction point; Retina; Xenopus laevis
Objectives. To compare pathologic outcomes after treatment with gemcitabine and cisplatin (GC) versus methotrexate, vinblastine, adriamycin, and cisplatin (MVAC) in the neoadjuvant setting. Methods. Data was retrospectively collected on 178 patients with T2-T4 bladder cancer who underwent radical cystectomy between 2003 and 2011. Outcomes of interest included those with complete response (pT0) and any response (≤pT1). Odds ratios were calculated using multivariate logistic regression. Results. Compared to those who did not receive neoadjuvant chemotherapy, there were more patients with complete response (28% versus 9%, OR 3.11 (95% CI: 1.45–6.64), P = 0.03) and any response (52% versus 25%, OR 3.23 (95% CI: 1.21–8.64), P = 0.01). Seventy-two patients received GC (n = 41) or MVAC (n = 31). CR was achieved in 29% and 22% of GC and MVAC patients, respectively (multivariate OR 0.39, 95% CI 0.10–1.58). Any response (≤pT1) was achieved in 56% of GC and 45% of MVAC patients (multivariate OR 0.45, 95% CI 0.12–1.71). Conclusions. We observed similar pathologic response rates for GC and MVAC neoadjuvant chemotherapy in this cohort of patients with muscle invasive urothelial cancer (MIBC). Our findings support the use of GC as an alternative regimen in the neoadjuvant setting.
The erythrocyte membrane content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which constitutes the omega‐3 index (O3I), predicts cardiovascular disease mortality. The amount of EPA+DHA needed to achieve a target O3I is poorly defined, as are the determinants of the O3I response to a change in EPA+DHA intake. The objective of this study was to develop a predictive model of the O3I response to EPA+DHA supplementation in healthy adults, specifically identifying factors that determine the response.
Methods and Results
A randomized, placebo‐controlled, double‐blind, parallel‐group study was conducted in 115 healthy men and women. One of 5 doses (0, 300, 600, 900, 1800 mg) of EPA+DHA was given daily as placebo or fish oil supplements for ≈5 months. The O3I was measured at baseline and at the end of the study. There were no significant differences in the clinical characteristics between the groups at baseline. The O3I increased in a dose‐dependent manner (P<0.0001), with the dose of EPA+DHA alone accounting for 68% (quadratic, P<0.0001) of the variability in the O3I response. Dose adjusted per unit body weight (g/kg) accounted for 70% (linear, P<0.0001). Additional factors that improved prediction of treatment response were baseline O3I, age, sex, and physical activity. Collectively, these explained 78% of the response variability (P<0.0001).
Our findings validate the O3I as a biomarker of EPA+DHA consumption and identify additional factors, particularly body weight, that can be used to tailor EPA+DHA recommendations to achieve a target O3I.
blood cell; fatty acids; fish oil; metabolism; nutrition
Edge wear is an adverse factor that can negatively impact certain THAs. In some metal-on-metal THAs, it can lead to adverse tissue reactions including aseptic lymphocytic vasculitis-associated lesions and even to pseudotumor formation. In some ceramic-on-ceramic THAs, it can lead to squeaking and/or stripe wear. Edge wear in metal-on-metal and ceramic-on-ceramic THAs can also be associated with accelerated wear across the articulation of these joints.
I asked: Does edge wear occur in metal-on-polyethylene (MOP) articulations? And if so, does it increase joint wear?
I examined the evidence in the literature for edge wear occurring in MOP THA and then assessed the evidence in the literature for data supporting the concept that edge wear in MOP hips could accelerate wear across the articulation over time.
Extensive data in the literature confirm edge wear is common in MOP THA. Surprisingly, the evidence does not support that it accelerates wear across the articulation. In fact, substantial data support the concept that it does not.
These observations suggest, in terms of edge wear accelerating overall wear, MOP articulation may have a privileged position compared to hard-on-hard THA articulations.
The metabolic syndrome includes both dyslipidemia and impaired vascular function.
Because extended-release niacin (ERN) and prescription omega-3 acid ethyl-esters
(P-OM3) independently improve these characteristics, we tested their effects in
combination. Sixty metabolic syndrome subjects were randomized to 16 weeks of
treatment on dual placebo, P-OM3 (4g/day), ERN (2 g/day), or combination in a
double-blind trial. Lipoprotein subfractions and vascular endpoints were measured and
tested using ANCOVA. ERN increased HDL cholesterol by 5.4 mg/dl from baseline
(P = 0.04), decreased triglycerides (TG) by 39 mg/dl
(−21%, P = 0.003), and decreased the augmentation
index, which is a measure of vascular stiffness, by 3.5 units (P
= 0.04). P-OM3 reduced TG by 26 mg/dl (−13%, P =
0.04). Combination treatment increased HDL cholesterol by 7.8 mg/dl
(P = 002) and decreased TG by 72 mg/dl (−34%) but
there was no improvement in vascular stiffness. Detailed analysis of lipoprotein
subfractions revealed increased large, bouyant HDL2 (3.3 mg/dl;
P = 0.002) and decreased VLDL1+2
(−32%; P < 0.0001), among subjects treated with combination
therapy, that were not present with either therapy alone. ERN and P-OM3 alone
improved characteristics of metabolic syndrome; however, whereas subjects on
combination therapy did not have improved vascular stiffness, TG and HDL levels
improved as did certain lipoprotein subfractions.
fish oil; niacin; metabolic syndrome; very low density lipoprotein; high density lipoprotein; arterial stiffness; augmentation index; eicosapentaenoic acid; docosahexaenoic acid
During chick gastrulation, inhibition of BMP signaling is required for primitive streak formation and induction of Hensen’s node. We have identified a unique secreted protein, Tsukushi (TSK), which belongs to the Small Leucine-Rich Proteoglycan (SLRP) family and is expressed in the primitive streak and Hensen’s node. Grafts of cells expressing TSK in combination with the middle primitive streak induce an ectopic Hensen’s node, while electroporation of TSK siRNA inhibits induction of the node. In Xenopus embryos, TSK can block BMP function and induce a secondary dorsal axis, while it can dorsalize ventral mesoderm and induce neural tissue in embryonic explants. Biochemical analysis shows that TSK binds directly to both BMP and chordin and forms a ternary complex with them. These observations indicate that TSK is an essential dorsalizing factor involved in the induction of Hensen’s node.
Autosomal recessive primary microcephaly (MCPH) is a congenital disorder characterized by significantly reduced brain size and mental retardation. Nine genes are currently known to be associated with the condition, all of which encode centrosomal or spindle pole proteins. MCPH is associated with a reduction in proliferation of neural progenitors during fetal development. The cellular mechanisms underlying the proliferation defect, however, are not fully understood. The zebrafish retinal neuroepithelium provides an ideal system to investigate this question. Mutant or morpholino-mediated knockdown of three known MCPH genes (stil, aspm and wdr62) and a fourth centrosomal gene, odf2, which is linked to several MCPH proteins, results in a marked reduction in head and eye size. Imaging studies reveal a dramatic rise in the fraction of proliferating cells in mitosis in all cases, and time-lapse microscopy points to a failure of progression through prometaphase. There was also increased apoptosis in all the MCPH models but this appears to be secondary to the mitotic defect as we frequently saw mitotically arrested cells disappear, and knocking down p53 apoptosis did not rescue the mitotic phenotype, either in whole retinas or clones.
zebrafish retina; microcephaly; STIL; ASPM; WDR62; ODF2
Long‐chain polyunsaturated omega‐3 fatty acids (n‐3 PUFA) demonstrated antiarrhythmic potential in experimental studies. In a large multinational randomized trial (OPERA), perioperative fish oil supplementation did not reduce the risk of postoperative atrial fibrillation (PoAF) in cardiac surgery patients. However, whether presupplementation habitual plasma phospholipid n‐3 PUFA, or achieved or change in n‐3 PUFA level postsupplementation are associated with lower risk of PoAF is unknown.
Methods and Results
In 564 subjects undergoing cardiac surgery between August 2010 and June 2012 in 28 centers across 3 countries, plasma phospholipid levels of eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) were measured at enrollment and again on the morning of cardiac surgery following fish oil or placebo supplementation (10 g over 3 to 5 days, or 8 g over 2 days). The primary endpoint was incident PoAF lasting ≥30 seconds, centrally adjudicated, and confirmed by rhythm strip or ECG. Secondary endpoints included sustained (≥1 hour), symptomatic, or treated PoAF; the time to first PoAF; and the number of PoAF episodes per patient. PoAF outcomes were assessed until hospital discharge or postoperative day 10, whichever occurred first. Relative to the baseline, fish oil supplementation increased phospholipid concentrations of EPA (+142%), DPA (+13%), and DHA (+22%) (P<0.001 each). Substantial interindividual variability was observed for change in total n‐3 PUFA (range=−0.7% to 7.5% after 5 days of supplementation). Neither individual nor total circulating n‐3 PUFA levels at enrollment, morning of surgery, or change between these time points were associated with risk of PoAF. The multivariable‐adjusted OR (95% CI) across increasing quartiles of total n‐3 PUFA at enrollment were 1.0, 1.06 (0.60 to 1.90), 1.35 (0.76 to 2.38), and 1.19 (0.64 to 2.20); and for changes in n‐3 PUFA between enrollment and the morning of surgery were 1.0, 0.78 (0.44 to 1.39), 0.89 (0.51 to 1.55), and 1.01 (0.58 to 1.75). In stratified analysis, demographic, medication, and cardiac parameters did not significantly modify these associations. Findings were similar for secondary PoAF endpoints.
Among patients undergoing cardiac surgery, neither higher habitual circulating n‐3 PUFA levels, nor achieved levels or changes following short‐term fish oil supplementation are associated with risk of PoAF.
Clinical Trial Registration
URL: Clinicaltrials.gov Unique identifier: NCT00970489
biomarker; cardiac surgery; omega‐3 fatty acids; postoperative atrial fibrillation; randomized controlled trial
Engrailed-2 (En-2), a homeodomain transcription factor, is expressed in a caudal-to-rostral gradient in the developing mid-brain, where it has an instructive role in patterning the optic tectum—the target of topographic retinal input1,2. In addition to its well-known role in regulating gene expression through its DNA-binding domain, En-2 may also have a role in cell–cell communication, as suggested by the presence of other domains involved in nuclear export, secretion and internalization3. Consistent with this possibility, here we report that an external gradient of En-2 protein strongly repels growth cones of Xenopus axons originating from the temporal retina and, conversely, attracts nasal axons. Fluorescently tagged En-2 accumulates inside growth cones within minutes of exposure, and a mutant form of the protein that cannot enter cells fails to elicit axon turning. Once internalized, En-2 stimulates the rapid phosphorylation of proteins involved in translation initiation and triggers the local synthesis of new proteins. Furthermore, the turning responses of both nasal and temporal growth cones in the presence of En-2 are blocked by inhibitors of protein synthesis. The differential guidance of nasal and temporal axons reported here suggests that En-2 may participate directly in topographic map formation in the vertebrate visual system.
TGF-β, a mediator of pulmonary fibrosis, is a genetic modifier of CF respiratory deterioration. The mechanistic relationship between TGF-β signaling and CF lung disease has not been determined.
To investigate myofibroblast differentiation in CF lung tissue as a novel pathway by which TGF-β signaling may contribute to pulmonary decline, airway remodeling and tissue fibrosis.
Lung samples from CF and non-CF subjects were analyzed morphometrically for total TGF-β1, TGF-β signaling (Smad2 phosphorylation), myofibroblast differentiation (α-smooth muscle actin), and collagen deposition (Masson trichrome stain).
TGF-β signaling and fibrosis are markedly increased in CF (p<0.01), and the presence of myofibroblasts is four-fold higher in CF vs. normal lung tissue (p<0.005). In lung tissue with prominent TGF-β signaling, both myofibroblast differentiation and tissue fibrosis are significantly augmented (p<0.005).
These studies establish for the first time that a pathogenic mechanism described previously in pulmonary fibrosis is also prominent in cystic fibrosis lung disease. The presence of TGF-β dependent signaling in areas of prominent myofibroblast proliferation and fibrosis in CF suggests that strategies under development for other pro-fibrotic lung conditions may also be evaluated for use in CF.
Cell adhesion molecules and diffusible cues both regulate axon pathfinding, yet how these two modes of signalling interact is poorly understood. The homophilic cell adhesion molecule, NF-protocadherin (NFPC) is expressed in the mid-dorsal optic tract neuroepithelium and in the axons of developing retinal ganglion cells (RGC). Here we report that targeted disruption of NFPC function in RGC axons or the optic tract neuroepithelium results in unexpectedly localized pathfinding defects in the mid-optic tract. Sema3A, which lies adjacent to this turn, stimulates rapid protein synthesis-dependent increases in growth cone NFPC and its cofactor, TAF1, in vitro. In vivo, growth cones exhibit marked increases in NFPC translation reporter activity in this mid-optic tract region that are attenuated by blocking Neuropilin-1 function. Our results suggest that translation-linked coupling between regionally localised diffusible cues and cell adhesion can help axons navigate discrete segments of the pathway.
Childhood obesity is a significant risk factor for cardiovascular disease in adulthood. Although ventricular remodeling has been reported in obese youth, early tissue‐level markers within the myocardium that precede organ‐level alterations have not been described.
Methods and Results
We studied 21 obese adolescents (mean age, 17.7±2.6 years; mean body mass index [BMI], 41.9±9.5 kg/m2, including 11 patients with type 2 diabetes [T2D]) and 12 healthy volunteers (age, 15.1±4.5 years; BMI, 20.1±3.5 kg/m2) using biomarkers of cardiometabolic risk and cardiac magnetic resonance imaging (CMR) to phenotype cardiac structure, function, and interstitial matrix remodeling by standard techniques. Although left ventricular ejection fraction and left atrial volumes were similar in healthy volunteers and obese patients (and within normal body size‐adjusted limits), interstitial matrix expansion by CMR extracellular volume fraction (ECV) was significantly different between healthy volunteers (median, 0.264; interquartile range [IQR], 0.253 to 0.271), obese adolescents without T2D (median, 0.328; IQR, 0.278 to 0.345), and obese adolescents with T2D (median, 0.376; IQR, 0.336 to 0.407; P=0.0001). ECV was associated with BMI for the entire population (r=0.58, P<0.001) and with high‐sensitivity C‐reactive protein (r=0.47, P<0.05), serum triglycerides (r=0.51, P<0.05), and hemoglobin A1c (r=0.76, P<0.0001) in the obese stratum.
Obese adolescents (particularly those with T2D) have subclinical alterations in myocardial tissue architecture associated with inflammation and insulin resistance. These alterations precede significant left ventricular hypertrophy or decreased cardiac function.
CT or MRI; obesity; type 2 diabetes
The eye is a peripheral outpost of the central nervous system (CNS) where the retinal ganglion cells (RGCs) reside. RGC axons navigate to their targets in a remarkably stereotyped and error-free manner and it is this process of directed growth that underlies the complex organization of the adult brain. The RGCs are the only retinal neurons to project into the brain and their peripheral location makes them an unusually accessible population of projection neurons for experiments involving in vivo gene transfer, anatomical tracing, transplantation and in vitro culture. In this paper, we review recent findings that have contributed to our understanding of some of the guidance decisions that axons make in the developing visual system. We look at two choice points in the pathway, the optic nerve head (onh) and the midline chiasm, and discuss evidence that supports the idea that key molecules in guiding axon growth at these junctures are netrin-1 (onh) and ephrin-B (chiasm). In the optic tectum where RGC axon terminals are arrayed in topographic order, we present experimental evidence to suggest that in the dorso-ventral dimension, the B-type ephrins and Eph receptors are of prime importance, possibly through attractive interactions. This complements the anterior-posterior topographic mapping known to be mediated through A-type ephrin/Eph repulsive interactions. An emerging theme is that guidance molecules such as ephrin-B and netrin-1 have complex patterns of restricted expression in the pathway and play multiple and changing roles in axon guidance.
retina; axon guidance; netrin; Eph receptor; ephrin
It has been proposed that growth cones navigating through gradients adapt to baseline concentrations of guidance cues. This adaptation process is poorly understood. Using the collapse assay, we show that adaptation in Xenopus laevis retinal growth cones to the guidance cues Sema3A or netrin-1 involves two processes: a fast, ligand-specific desensitization that occurs within 2 min of exposure and is dependent on endocytosis, and a slower, ligand-specific resensitization, which occurs within 5 min and is dependent upon protein synthesis. These two phases of adaptation allow retinal axons to adjust their range of sensitivity to specific guidance cues.
In Xenopus tadpoles, all retinal ganglion cells (RGCs) send axons contralaterally across the optic chiasm. At metamorphosis, a subpopulation of EphB-expressing RGCs in the ventrotemporal retina begin to project ipsilaterally. However, when these metamorphic RGCs are grafted into embryos, they project contralaterally, suggesting that the embryonic chiasm lacks signals that guide axons ipsilaterally. Ephrin-B is expressed discretely at the chiasm of metamorphic but not premetamorphic Xenopus. When expressed prematurely in the embryonic chiasm, ephrin-B causes precocious ipsilateral projections from the EphB-expressing RGCs. Ephrin-B is also found in the chiasm of mammals, which have ipsilateral projections, but not in the chiasm of fish and birds, which do not. These results suggest that ephrin-B/EphB interactions play a key role in the sorting of axons at the vertebrate chiasm.
Recent clinical studies that evaluated the effects of supplemental omega-3 polyunsaturated fatty acids (n-3 PUFAs) on sudden cardiac death have yielded conflicting results. Our aim was to clarify this issue using an established and clinical relevant canine model of sudden cardiac death.
Methods and Results
Susceptibility to ventricular fibrillation (VF) was evaluated using a 2 minute left circumflex artery occlusion during the last minute of an exercise test in 76 dogs (from two independent studies) with healed myocardial infarctions (MI); 44 developed VF (susceptible, VF+) while 32 did not (resistant, VF−). These dogs were then randomly assigned to either placebo (1 g/day, corn oil; 15 VF+, 11 VF−) or n-3 PUFA (1–4 g/day, docosahexaenoic acid + eicosapentaenoic acid ethyl esters, 29 VF+, 21 VF−) groups. Seven sham (no-MI) dogs were also treated with n-3 PUFA (4 g/day). After treatment (3 months), the exercise + ischemia test was repeated. Dietary n-3 PUFAs produced significant (P<0.01) increases in red blood cell and left ventricular n-3 PUFA levels. Nine post MI (5 placebo vs. 4 n-3 PUFA) and 2 sham dogs died suddenly during the 3-month treatment period. The n-3 PUFA treatment failed to prevent arrhythmias in VF+ dogs (decreased in 27% placebo vs. 24% n-3 PUFA, P=0.5646) but induced VT/VF in VF− animals (n-3 PUFA 33% vs. placebo 0%, P=0.0442).
Despite large increases in cardiac tissue n-3 PUFA content, dietary n-3 PUFAs did not prevent ischemia-induced VF and actually increased arrhythmia susceptibility in both non-infarcted and low risk post-MI dogs.
omega-3 polyunsaturated fatty acids; fish oil; ventricular fibrillation; myocardial ischemia; myocardial infarction
Omega-3 fatty acids reduced heart rate (HR) and blood pressure (BP) in some studies, but dose–response studies are rare, and little is known about underlying mechanisms.
We examined effects of 0.85 g/day eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) (low dose) and 3.4 g/day EPA + DHA (high dose) on HR and systemic hemodynamics during rest, speech, and foot cold pressor tasks.
This was a dose–response, placebo-controlled, double-blind, randomized, crossover trial (8-week treatment, 6-week washout) in 26 adults.
Throughout the testing sessions, HR was reduced in a dose-dependent manner. The high dose reduced BP and stroke volume and increased pre-ejection period. Reductions in BP were associated with increases in erythrocyte omega-3 fatty acids.
High-dose long-chain omega-3 fatty acids can reduce BP and HR, at rest and during stress. These findings suggest that at-risk populations may achieve benefits with increased omega-3 intake.
Omega-3; Fish; Hemodynamics; Acute stress
Long chain omega-3 fatty acids (FAs) are effective for reducing plasma triglyceride (TG) levels. At the pharmaceutical dose, 3.4 g/day, they reduce plasma TG by about 25-50% after one month of treatment, resulting primarily from the decline in hepatic very low density lipoprotein (VLDL-TG) production, and secondarily from the increase in VLDL clearance. Numerous mechanisms have been shown to contribute to the TG overproduction, but a key component is an increase in the availability of FAs in the liver. The liver derives FAs from three sources: diet (delivered via chylomicron remnants), de novo lipogenesis, and circulating non-esterified FAs (NEFAs). Of these, NEFAs contribute the largest fraction to VLDL-TG production in both normotriglyceridemic subjects and hypertriglyceridemic, insulin resistant patients. Thus reducing NEFA delivery to the liver would be a likely locus of action for fish oils (FO). The key regulator of plasma NEFA is intracellular adipocyte lipolysis via hormone sensitive lipase (HSL), which increases as insulin sensitivity worsens. FO counteracts intracellular lipolysis in adipocytes by suppressing adipose tissue inflammation. In addition, FO increases extracellular lipolysis by lipoprotein lipase (LpL) in adipose, heart and skeletal muscle and enhances hepatic and skeletal muscle β-oxidation which contributes to reduced FA delivery to the liver. FO could activate transcription factors which control metabolic pathways in a tissue specific manner regulating nutrient traffic and reducing plasma TG.
fish oil; omega-3; plasma triglycerides; lipolysis; NEFA; eicosapentaenoic acid; docosahexaenoic acid
Within the developing vertebrate retina, particular subtypes of amacrine cells (ACs) tend to arise from progenitors expressing the bHLH transcription factor, Atoh7, which is necessary for the early generation of retinal ganglion cells (RGCs). All ACs require the post-mitotic expression of the bHLH transcription factor Ptf1a, however Ptf1a alone is not sufficient to give subtype identities. Here we use functional and in vivo time-lapse studies in the zebrafish retina to investigate on the developmental programs leading to ACs specification within the subsequent divisions of Atoh7-positive progenitors. We find evidences that the homeobox transcription factor Barhl2 is an AC subtype identity-biasing factor that turns on within Atoh7-positive descendants. In vivo lineage tracing reveals that particular modes of cell division tend to generate Barhl2-positive precursors from sisters of RGCs. Additionally, Atoh7 indirectly impacts these division modes to regulate the right number of barhl2-expressing cells. We finally find that Atoh7 itself influences the subtypes of Barhl2-dependent ACs. Taken together, our study uncovers lineage-related and molecular logic of subtype specification in the vertebrate retina, by showing that specific AC subtypes arise via a particular mode of cell division and a transcriptional network cascade involving the sequential expression of first atoh7 followed by ptf1a and then barhl2.
fate determination; cell lineage; Barhl2; subtype specification; retina; zebrafish
Several studies have successfully produced a variety of neural cell types from human embryonic stem cells (hESCs), but there has been limited systematic analysis of how different regional identities are established using well-defined differentiation conditions. We have used adherent, chemically defined cultures to analyse the roles of Activin/Nodal, bone morphogenetic protein (BMP), fibroblast growth factor (FGF) and Wnt/β-catenin signalling in neural induction, anteroposterior patterning and eye field specification in hESCs. We show that either BMP inhibition or activation of FGF signalling is required for effective neural induction, but these two pathways have distinct outcomes on rostrocaudal patterning. While BMP inhibition leads to specification of forebrain/midbrain positional identities, FGF-dependent neural induction is associated with strong posteriorization towards hindbrain/spinal cord fates. We also demonstrate that Wnt/β-catenin signalling is activated during neural induction and promotes acquisition of neural fates posterior to forebrain. Therefore, inhibition of this pathway is needed for efficient forebrain specification. Finally, we provide evidence that the levels of Activin/Nodal and BMP signalling have a marked influence on further forebrain patterning and that constitutive inhibition of these pathways represses expression of eye field genes. These results show that the key mechanisms controlling neural patterning in model vertebrate species are preserved in adherent, chemically defined hESC cultures and reveal new insights into the signals regulating eye field specification.
human embryonic stem cells; neuroectoderm; anteroposterior patterning; forebrain; eye field
Red blood cell (RBC) levels of eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA, the omega-3 index, expressed as a percent of total fatty acids) are inversely related to risk for cardiovascular disease (CVD). Although several mechanisms underlying this relationship have been proposed, understanding the associations between the omega-3 index and markers of CVD in the community can shed additional light on this question. The objectives of this study were to define the relations between the omega-3 index and clinical factors and to determine the heritability of the omega-3 index.
RBC samples (n = 3196) drawn between 2005 and 2008 from participants in the Framingham Study [Examination 8 of the Offspring cohort plus Examination 3 of the Omni (minorities) cohort] were analyzed for fatty acid composition by gas chromatography.
The mean (SD) omega-3 index was 5.6% (1.7%). In multivariable regression models, the factors significantly and directly associated with the omega-3 index were age, female sex, higher education, fish oil supplementation, dietary intake of EPA + DHA, aspirin use, lipid pharmacotherapy, and LDL-cholesterol. Factors inversely associated were Offspring cohort, heart rate, waist girth, triglycerides and smoking. The total explained variability in the omega-3 index for the fully adjusted model was 73%, which included major components due to heritability (24%), EPA + DHA intake (25%), and fish oil supplementation (15%).
The variability in the omega-3 index is determined primarily by dietary and genetic factors. An increased omega-3 index is associated with a generally cardioprotective risk factor milieu.
Epidemiology; Cardiovascular disease; Risk factors; Omega-3 fatty acids; Erythrocytes; Heritability
To determine the extent to which levels of membrane eicosapentaenoic (EPA)+docosahexaenoic acids (DHA) (the omega-3 index) were associated with depression in patients with acute coronary syndrome (ACS). Depression is associated with worse cardiovascular (CV) outcomes in patients with ACS. Reduced levels of blood cell membrane omega-3 (n-3) fatty acids (FAs), an emerging risk factor for both CV disease and depression, may help to explain the link between depression and adverse CV outcomes.
We measured membrane FA composition in 759 patients with confirmed ACS. The analysis included not only EPA and DHA but also the n-6 FAs linoleic and arachidonic acids (LA and AA). Depressive symptoms were measured with the Patient Health Questionnaire-9 (PHQ). Multivariable linear regression was used to adjust for demographic and clinical characteristics.
There was a significant inverse relationship between the n-3 index and depressive symptoms (PHQ) in the fully adjusted model (p = .034). For every 4.54% point rise in the n-3 index, there was a 1-point decline in depressive symptoms. In contrast to the n-3 FAs, membrane levels of the n-6 FAs LA and AA were not different between depressed and nondepressed ACS patients.
We found an inverse relationship between the n-3 index and the prevalence of depressive symptoms in patients with ACS. Therefore, this study supports the hypothesis that reduced n-3 FA tissue levels are a common and potentially modifiable link between depression and adverse CV outcomes.
depression; acute coronary syndrome; omega-3 fatty acids
How synaptic neuropil is formed within the CNS is poorly understood. The retinal inner plexiform layer (IPL) is positioned between the cell bodies of amacrine cells (ACs) and retinal ganglion cells (RGCs). It consists of bipolar cell (BC) axon terminals that synapse on the dendrites of ACs and RGCs intermingled with projections from Müller glia (MG). We examined whether any of these cellular processes are specifically required for the formation of the IPL. Using genetic and pharmacological strategies, we eliminated RGCs, ACs, and MG individually or in combination. Even in the absence of all of these partner cells, an IPL-like neuropil consisting of only BC axon terminals still forms, complete with presynaptic specializations and sublaminar organization. Previous studies have shown that an IPL can form in the complete absence of BCs; therefore, we conclude that neither presynaptic nor postsynaptic processes are individually essential for the formation of this synaptic neuropil.
► Bipolar cells are among the first cell types to colonize the nascent IPL ► Presynaptic BCs can autonomously build an IPL-like neuropil ► The BC-only neuropil exhibits sublaminar structure and presynaptic specializations ► No single contributing cell type is essential for the formation of the IPL
There has been little work on the cellular requirements for the formation of synaptic neuropil. In studying the development of the retinal inner plexiform layer (IPL), Harris and colleagues demonstrate that the axons of retinal interneurons, bipolar cells, will form a neuropil in the absence of all partner cells in vivo. These results suggest that neuropil formation in the vertebrate CNS may not require interactions between cell types but instead may result from the coordinated action of multiple autonomously stratifying cell types.
Unlike healthy adult tissues, cancers produce energy mainly by aerobic glycolysis instead of oxidative phosphorylation1. This adaptation, called the Warburg effect, may be a feature of all dividing cells, both normal and cancerous2, or it may be specific to cancers3. Whether in a normally growing tissue during development, proliferating and postmitotic cells produce energy in fundamentally different ways is not known. Here we show in the embryonic Xenopus retina in vivo, that dividing progenitor cells depend less on oxidative phosphorylation for ATP production than non-dividing differentiated cells, and instead use glycogen to fuel aerobic glycolysis. The transition from glycolysis to oxidative phosphorylation is connected to the cell differentiation process. Glycolysis is indispensable for progenitor proliferation and biosynthesis, even when it is not used for ATP production. These results suggest that the Warburg effect can be a feature of normal proliferation in vivo, and that the regulation of glycolysis and oxidative phosphorylation is critical for normal development.