Basal delamination during mouse gastrulation primes pluripotent cells for differentiation

The blueprint of the mammalian body plan is laid out during gastrulation, when a trilaminar embryo is formed. This process entails a burst of proliferation, the ingression of embryonic epiblast cells at the primitive streak, and their priming toward primitive streak fates. How these different events are coordinated remains unknown. Here, we developed and characterized a 3D culture of self-renewing mouse embryonic cells that captures the main transcriptional and architectural features of the early gastrulating mouse epiblast. Using this system in combination with microfabrication and in vivo experiments, we found that proliferation-induced crowding triggers delamination of cells that express high levels of the apical polarity protein aPKC. Upon delamination, cells become more sensitive to Wnt signaling and upregulate the expression of primitive streak markers such as Brachyury. This mechanistic coupling between ingression and differentiation ensures that the right cell types become specified at the right place during embryonic development.

Tissue morphology influences the temporal program of human brain organoid development

Progression through fate decisions determines cellular composition and tissue architecture, but how that same architecture may impact cell fate is less clear. We took advantage of organoids as a tractable model to interrogate this interaction of form and fate. Screening methodological variations revealed that common protocol adjustments impacted various aspects of morphology, from macrostructure to tissue architecture. We examined the impact of morphological perturbations on cell fate through integrated single nuclear RNA sequencing (snRNA-seq) and spatial transcriptomics. Regardless of the specific protocol, organoids with more complex morphology better mimicked in vivo human fetal brain development. Organoids with perturbed tissue architecture displayed aberrant temporal progression, with cells being intermingled in both space and time. Finally, encapsulation to impart a simplified morphology led to disrupted tissue cytoarchitecture and a similar abnormal maturational timing. These data demonstrate that cells of the developing brain require proper spatial coordinates to undergo correct temporal progression.

The architecture of Cidec-mediated interfaces between lipid droplets

Lipid droplets (LDs) are intracellular organelles responsible for storing surplus energy as neutral lipids. Their size and number vary enormously. In white adipocytes, LDs can reach 100 μm in diameter, occupying >90% of the cell. Cidec, which is strictly required for the formation of large LDs, is concentrated at interfaces between adjacent LDs and facilitates directional flux of neutral lipids from the smaller to the larger LD. The mechanism of lipid transfer is unclear, in part because the architecture of interfaces between LDs remains elusive. Here we visualize interfaces between LDs by electron cryo-tomography and analyze the kinetics of lipid transfer by quantitative live fluorescence microscopy. We show that transfer occurs through closely apposed monolayers, is slowed down by increasing the distance between the monolayers, and follows exponential kinetics. Our data corroborate the notion that Cidec facilitates pressure-driven transfer of neutral lipids through two "leaky" monolayers between LDs.

Ultrastructure of COPII vesicle formation in yeast characterized by correlative light and electron microscopy

Traffic of proteins out of the endoplasmic reticulum (ER) is driven by the COPII coat, a layered protein scaffold that mediates the capture of cargo proteins and the remodeling of the ER membrane into spherical vesicular carriers. Although the components of this machinery have been genetically defined, and the mechanisms of coat assembly extensively explored in vitro, understanding the physical mechanisms of membrane remodeling in cells remains a challenge. Here we use correlative light and electron microscopy (CLEM) to visualize the nanoscale ultrastructure of membrane remodeling at ER exit sites (ERES) in yeast cells. Using various COPII mutants, we have determined the broad contribution that each layer of the coat makes to membrane remodeling. Our data suggest that inner coat components define the radius of curvature, whereas outer coat components facilitate membrane fission. The organization of the coat in conjunction with membrane biophysical properties determines the ultrastructure of vesicles and thus the efficiency of protein transport.

Usefulness of non-invasive myocardial work to predict left ventricular recovery and acute complications after acute anterior myocardial infarction treated by primary angioplasty

Background

Predicting left ventricular (LV) recovery after acute ST-elevation myocardial infarction (STEMI) is challenging and of prognostic importance.

Objective

To evaluate the usefulness of non-invasive myocardial work (MW), a new index of global and regional myocardial performance, to predict LV recovery and in-hospital complications after STEMI.

Methods

Ninety-three consecutive patients with anterior STEMI (mean age, 59±12 years) treated by primary angioplasty underwent transthoracic echocardiography (TTE) within 24–48 hours after angioplasty and a median of 92 days at follow-up. MW is derived from the non-invasive strain-pressure loop obtained from the 2D strain data, integrating in its calculation the non-invasive brachial arterial pressure. Segmental LV recovery was defined as a normalization of segmental wall motion abnormalities of the affected segments and global recovery as an absolute improvement of left ventricular ejection fraction (LVEF) greater than 5% in patients with baseline LVEF <50%. In-hospital complications were defined as a composite of death, reinfarction, heart failure, and LV apical thrombus.

Results

1642 segments were studied and MW was impaired in infarct segments, more severely in no recovery versus recovery segments (MW index, constructive MW, MW efficiency, all, p<0.01). Furthermore, global MW was significantly correlated to acute and follow-up LVEF and global longitudinal strain (GLS) (all, p<0.01). Constructive MW was the best indice to predict segmental (p<0.01 versus MW index, MW efficiency, and wasted work), and global recovery (p<0.05 versus GLS) with an independent association (all, p<0.01). Moreover, global constructive MW was independently associated to in-hospital complications which occurred in 18 patients (p<0.01).

Conclusion

In patients with anterior STEMI treated by primary angioplasty, acute constructive MW is an independent predictor of segmental and global LV recovery, as well as in-hospital complications.

Funding Acknowledgement

Type of funding source: None

Membrane characteristics tune activities of endosomal and autophagic human VPS34 complexes

The lipid kinase VPS34 orchestrates diverse processes, including autophagy, endocytic sorting, phagocytosis, anabolic responses and cell division. VPS34 forms various complexes that help adapt it to specific pathways, with complexes I and II being the most prominent ones. We found that physicochemical properties of membranes strongly modulate VPS34 activity. Greater unsaturation of both substrate and non-substrate lipids, negative charge and curvature activate VPS34 complexes, adapting them to their cellular compartments. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) of complexes I and II on membranes elucidated structural determinants that enable them to bind membranes. Among these are the Barkor/ATG14L autophagosome targeting sequence (BATS), which makes autophagy-specific complex I more active than the endocytic complex II, and the Beclin1 BARA domain. Interestingly, even though Beclin1 BARA is common to both complexes, its membrane-interacting loops are critical for complex II, but have only a minor role for complex I.

Tricalbins Contribute to Cellular Lipid Flux and Form Curved ER-PM Contacts that Are Bridged by Rod-Shaped Structures

Lipid flow between cellular organelles occurs via membrane contact sites. Extended-synaptotagmins, known as tricalbins in yeast, mediate lipid transfer between the endoplasmic reticulum (ER) and plasma membrane (PM). How these proteins regulate membrane architecture to transport lipids across the aqueous space between bilayers remains unknown. Using correlative microscopy, electron cryo-tomography, and high-throughput genetics, we address the interplay of architecture and function in budding yeast. We find that ER-PM contacts differ in protein composition and membrane morphology, not in intermembrane distance. In situ electron cryo-tomography reveals the molecular organization of tricalbin-mediated contacts, suggesting a structural framework for putative lipid transfer. Genetic analysis uncovers functional overlap with cellular lipid routes, such as maintenance of PM asymmetry. Further redundancies are suggested for individual tricalbin protein domains. We propose a modularity of molecular and structural functions of tricalbins and of their roles within the cellular network of lipid distribution pathways.

The left atrial function is transiently impaired in Tako-tsubo cardiomyopathy and associated to in-hospital complications: a prospective study using two-dimensional strain

Tako-tsubo cardiomyopathy (TTC) is characterized by the presence of transient left ventricular (LV) dysfunction. Whether left atrial (LA) function is also impaired in this setting is unclear. To assess prospectively LA peak systolic longitudinal strain (LAS) by two-dimensional strain at the acute phase of TTC and after recovery and its association with in-hospital complications. 40 patients with typical TTC (mean age 79.5 ± 10 years) underwent transthoracic-Doppler echocardiography at the acute phase and at follow-up (32 ± 18 days later), including the measurement of the LAS (mean of maximal strain from the 4-2 chamber views). A control group of 15 patients (75 ± 7 years, 13 women) without overt cardiovascular disease served as a comparative group. In-hospital complication was a composite of death, heart failure, cardiogenic shock, LV thrombus, and sustained ventricular arrhythmia. In the TTC group, LAS improved significantly between the two examinations from 15 ± 5.5% to 27 ± 8% (p < 0.01) whereas LA volume did not change (p = NS). In the control group LAS was 30 ± 4% (p < 0.01 vs. TTC acute phase, p = NS vs. TTC follow-up). In TTC, at the acute phase LAS was independently correlated to LV global longitudinal strain (LVGLS), and after recovery to E/e', and the change of LAS was independently correlated to the change of the LVGLS (all, p < 0.01). Furthermore LAS was independently correlated to in-hospital complications (p < 0.01). LA function (reservoir) is transiently impaired in TTC and associated to in-hospital complications. Furthermore, the improvement of LAS parallel the dynamic improvement of LVGLS suggests that TTC induces a transient global left heart dysfunction.

Apical rotation, a simplified index of left ventricular twist is independently linked to recovery after acute anterior myocardial infarction

BACKGROUND

It is unclear whether apical rotation (Ar), which in normal setting represents the dominant contributions to LV twist by comparison to basal rotation (Br), predicts viability in acute anterior myocardial infarction (AMI). Our objective was to test the usefulness of Ar as a simple index to predict LV recovery after AMI.

METHODS

Fourty-five consecutive patients (mean age 60±14 years, mean LVEF 44±7%) with first AMI treated successfully by primary angioplasty underwent prospectively a comprehensive transthoracic-Doppler echocardiography including analysis of Ar, Br, and LV twist by 2-dimensional speckle tracking, using a basal and apical short axis-views, within 24h after angioplasty and 3-6months later. Recovery was defined as: - the normalization of the wall motion of more than 50% of initial abnormal segments (R1) and; - absolute improvement of LVEF≥10% (R2).

RESULTS

A better correlation was found between Ar and LV twist at each stage of the disease than between Br and LV twist (acute phase, R=0.77 vs. R=0.35; follow-up, R=0.9 vs. R=0.3 [all, P<0.001 for Ar, and all, P≤0.05 for Br]). Furthermore, a better correlation was found between Ar and follow-up LVEF (R=0.57), wall motion score index (R=0.44), and global longitudinal strain (R=0.54) (all, P<0.001) than between LV twist and the same parameters (R=0.39; R=0.32; R=0.32 respectively, all P<0.05). (For Br, all, P=NS). Ar as well as LV twist were significantly associated with recovery (all, P<0.01) with an area under the curve (AUC) higher for the former than for the latter (R1, N=18: AUC-Ar=0.81 and AUC-LV twist=0.69, P=0.05; R2, N=19: AUC-Ar=0.82, AUC-LV twist=0.75, P=0.1). In multivariate analysis, Ar remained an independent predictor of recovery R1 and R2 instead of LV twist (all, P≤0.01). Using a ROC curve analysis, the best cut-off of Ar to predict recovery R2 was 6.5°, with Se=77% Sp=85%, P<0.001.

CONCLUSION

Apical rotation is an independent predictor of segmental and global LV recovery after anterior acute anterior myocardial infarction treated successfully by primary angioplasty.

Assessment of left anterior descending artery stenosis of intermediate severity by fractional flow reserve, instantaneous wave-free ratio and non-invasive coronary flow reserve

Assessment of the functional significance of left anterior descending coronary artery (LAD) stenosis of intermediate severity is challenging and often based on fractional flow reserve (FFR). The instantaneous wave-free ratio (IFR), a new vasodilator-free index of coronary stenosis severity, and non-invasive coronary flow reserve (CFR) by transthoracic Doppler echocardiography are also potentially useful. A direct comparison of FFR, IFR, and non-invasive CFR has never been performed. Our objective was to test the usefulness of non-invasive CFR by comparison to invasive FFR and IFR in patients with LAD stenosis of angiographic intermediate severity and stable coronary artery disease.

METHODS

Ninety-four stable consecutive patients (mean age, 68±10years; 19 women) with angiographic proximal or mid LAD stenosis of intermediate severity (40-70% diameter stenosis on quantitative coronary angiography), were prospectively studied. They underwent IFR that was calculated as a trans-lesion pressure ratio during a specific period of baseline diastole, FFR with intracoronary bolus adenosine (180μg), and CFR using intravenous adenosine (140μg/kg/min over 2min) in the distal part of the LAD, the same day. CFR was defined as hyperemic peak diastolic LAD flow velocity divided by baseline flow velocity and FFR as distal pressure divided by mean aortic pressure during maximal hyperemia.

RESULTS

The mean values of IFR, FFR, and CFR were 0.88±0.07, 0.81±0.09, and 2.4±0.6 respectively. A significant correlation was found between CFR and FFR (R=0.63, curvilinear relationship), FFR and IFR (R=0.6, linear relationship), and between CFR and IFR (R=0.5) (all, P<0.01). Using a ROC curve analysis, the best cut-off to detect a significant lesion based on FFR assessment (FFR≤0.8, N=31) was IFR≤0.88 with a sensitivity (Se) of 74%, specificity (Sp) of 73%, AUC 0.81±0.04; and CFR≤2 with a Se=77%, Sp=89%, AUC 0.88±0.04, (all, P<0.001). Based on these cut-offs, discordant results between CFR and FFR were observed in 14 cases (agreement 85%), between CFR and IFR in 26 cases (agreement 72%), and between IFR and FFR in 26 cases (agreement 72%).

CONCLUSION

In stable patients with LAD stenosis of intermediate severity, non-invasive CFR is a useful tool to detect a significant lesion based on FFR. Furthermore, there was a better correlation and agreement between CFR and FFR than with IFR.

Assessment of left anterior descending artery stenosis of intermediate severity by fractional flow reserve, instantaneous wave-free ratio, and non-invasive coronary flow reserve

To test the usefulness of non-invasive coronary flow reserve (CFR) by transthoracic Doppler echocardiography by comparison to invasive fractional flow reserve (FFR) and instantaneous wave-free ratio (IFR), a new vasodilator-free index of coronary stenosis severity, in patients with left anterior descending artery (LAD) stenosis of intermediate severity (IS) and stable coronary artery disease. 94 consecutive patients (mean age 68 ± 10 years) with angiographic LAD stenosis of IS (50-70 % diameter stenosis), were prospectively studied. IFR was calculated as a trans-lesion pressure ratio during the wave-free period in diastole; FFR as distal pressure divided by mean aortic pressure during maximal hyperemia (using 180 μg intracoronary adenosine); and CFR as hyperemic peak LAD flow velocity divided by baseline flow velocity using intravenous adenosine (140 μg/kg/min over 2 min). The mean values of IFR, FFR, and CFR were 0.88 ± 0.07, 0.81 ± 0.09, and 2.4 ± 0.6 respectively. A significant correlation was found between CFR and FFR (r = 0. 68), FFR and IFR (r = 0.6), and between CFR and IFR (r = 0.5) (all, p < 0.01). Using a ROC curve analysis, the best cut-off to detect a significant lesion based on FFR assessment (FFR ≤ 0.8, n = 31) was IFR ≤ 0.88 with a sensitivity (Se) of 74 %, specificity (Sp) of 73 %, AUC 0.81 ± 0.04, accuracy 72 %; and CFR ≤ 2 with a Se = 77 %, Sp = 89 %, AUC 0.88 ± 0.04, accuracy 85 % (all, p < 0.001). In stable patients with LAD stenosis of IS, non-invasive CFR is a useful tool to detect a significant lesion based on FFR. Furthermore, there was a better correlation between CFR and FFR than between CFR and IFR, and a trend to a better diagnostic performance for CFR versus IFR.

[Voluminous thrombus straddling the patent foramen oval in the setting of massive pulmonary embolism, treated successfully by surgery]

Paradoxical embolism is rarely demonstrated, often suggested, and the diagnosis has been largely presumptive in most cases. The patent foramen ovale (PFO) is an important predisposing anatomic factor for such a complication. We describe a case where a voluminous thrombus straddling the PFO was diagnosed by echocardiography including the 3D modality, in the setting of acute massive pulmonary embolism. The treatment is not codified in this setting, and the thrombus was successfully removed by surgery, associated with PFO closure, and anticoagulation.

Management of hypersensitivity to platinum- and taxane-based chemotherapy: cepo review and clinical recommendations

BACKGROUND

Although antineoplastic agents are critical in the treatment of cancer, they can potentially cause hypersensitivity reactions that can have serious consequences. When such a reaction occurs, clinicians can either continue the treatment, at the risk of causing a severe or a potentially fatal anaphylactic reaction, or stop the treatment, although it might be the only one available. The objective of the present work was to evaluate the effectiveness of methods used to prevent and treat hypersensitivity reactions to platinum- or taxane-based chemotherapy and to develop evidence-based recommendations.

METHODS

The scientific literature published to December 2013, inclusive, was reviewed.

RESULTS

Premedication with antihistamines, H2 blockers, and corticosteroids is not effective in preventing hypersensitivity reactions to platinum salts. However, premedication significantly reduces the incidence of hypersensitivity to taxanes. A skin test can generally be performed to screen for patients at risk of developing a severe reaction to platinum salts in the presence of grade 1 or 2 reactions, but skin testing does not appear to be useful for taxanes. A desensitization protocol allows for re-administration of either platinum- or taxane-based chemotherapy to some patients without causing severe hypersensitivity reactions.

CONCLUSIONS

Several strategies such as premedication, skin testing, and desensitization protocols are available to potentially allow for administration of platinum- or taxane-based chemotherapy to patients who have had a hypersensitivity reaction and for whom no other treatment options are available. Considering the available evidence, the Comité de l'évolution des pratiques en oncologie made recommendations for clinical practice in Quebec.

[Incidence, associated factors, and follow-up of hospital heart failure complicating acute anterior myocardial infarction successfully treated by primary angioplasty]

Heart failure (HF) complicating acute myocardial infarction (AMI) is of poor prognosis and is often associated with patient's characteristics and success of reperfusion strategies. However, few data is available regarding the high-risk subgroup of patients with anterior AMI treated successfully by primary angioplasty. The aim of the study was to assess the incidence, associated factors, and the future of HF occurring during hospitalisation, in the setting of anterior AMI treated successfully by primary angioplasty.

METHODS

Eighty-five consecutive patients with anterior AMI treated successfully by primary angioplasty (final angiographic TIMI flow grade=3, without residual stenosis) were included. Clinical, biochemical, angiographic, and echocardiographic data were prospectively collected and compared between patients with (Killip 2 and 3) and without HF during hospitalisation.

RESULTS

Fifteen patients had HF (18%) during hospitalisation and 70 did not. By comparison to patients without HF, patients with HF were more frequently diabetics, had troponin peak and CPK, leucocytes count, and fasting glucose higher, LVEF and wall motion score index in the left anterior descending territory (WMSi-lad) poorer, and a lower non-invasive coronary flow reserve (CFR) in the LAD 24hours after angioplasty (all, P<0.05). In multivariate analysis, fasting glucose, leucocytes count after angioplasty, CFR and WMSi-lad were independently associated with HF, even after adjusting with angiographic variables (all, P<0.05). At 6months, patients with HF had less recovery of LV function and higher frequency of adverse LV remodelling (58% versus 20%, P<0.01) by comparison to patients without HF.

CONCLUSION

In conclusion, HF is not uncommon even after successful primary angioplasty for anterior AMI (nearly one patient out of 5), is associated with hyperglycaemia and inflammation, a poor microvascular reperfusion, and left ventricular systolic function, and is more frequently complicated by adverse LV remodelling and lack of LV recovery.

Wavelet analysis for single molecule localization microscopy

Localization of single molecules in microscopy images is a key step in quantitative single particle data analysis. Among them, single molecule based super-resolution optical microscopy techniques require high localization accuracy as well as computation of large data sets in the order of 10(5) single molecule detections to reconstruct a single image. We hereby present an algorithm based on image wavelet segmentation and single particle centroid determination, and compare its performance with the commonly used gaussian fitting of the point spread function. We performed realistic simulations at different signal-to-noise ratios and particle densities and show that the calculation time using the wavelet approach can be more than one order of magnitude faster than that of gaussian fitting without a significant degradation of the localization accuracy, from 1 nm to 4 nm in our range of study. We propose a simulation-based estimate of the resolution of an experimental single molecule acquisition.

[Assessment of left ventricular twist mechanics by two-dimensional strain in severe aortic stenosis with preserved ejection fraction]

Left ventricular (LV) twist is increased in aortic stenosis (AS) and the hypothesis of a compensatory mechanism is suggested but not established. Our aim was to assess LV twist mechanics in severe AS (<1cm(2) or 0.6cm(2)/m(2)) with preserved LV ejection fraction (LVEF>50%), and to analyze its relationship with LV systolic longitudinal function, early impaired in this setting, LV diastolic function, and symptomatic status.

METHODS

Forty-five consecutive patients with severe AS and preserved LVEF (mean age 73±11 years, 47% female, LVEF 68±11%, 67% symptomatic) underwent a transthoracic echocardiography including a bidimensional strain analysis by speckle tracking method, and were compared to a control group matched for age and sex (n=15). Global longitudinal strain (GLS) was measured using the four, two, and three apical views, and LV twist mechanics from the basal and apical short axis views. LV twist was defined as the net difference between apical and basal rotation, and LV twisting and untwisting rate (in°/s) were derived from twist curves.

RESULTS

Peak apical rotation, LV twist (25±8° vs 20±6), as well as peak systolic and diastolic apical rotation rate, and peak LV twisting rate were significantly higher in patients with AS when compared to controls (all, P<0.05), whereas, the other parameters of LV twist mechanics including basal rotation, were not significantly different between groups. By contrast, the GLS was significantly lower in patients with AS when compared to controls (-17.9±4 vs -20.5±2%, P<0.01). In addition, the GLS was significantly correlated to LV torsion (r=-0.42, P<0.01). Moreover, LV twist progressively impaired with the worsening of diastolic dysfunction and with symptoms onset.

CONCLUSION

LV twist is increased in severe AS with preserved LVEF, compensating the impairment of systolic longitudinal function. However, above a certain threshold LV twist deteriorates, attesting the failure of the compensatory mechanisms, leading to advanced diastolic dysfunction and symptom onset.

[Influence of leukocytes on coronary flow reserve, left ventricular systolic function, and in-hospital events, in patients with acute anterior myocardial infarction treated by primary angioplasty]

OBJECTIVE

To assess the relationship between leukocyte count, non invasive coronary flow reserve (CFR), left ventricular systolic function, and in-hospital adverse events in acute anterior myocardial infarction (AMI) treated by primary angioplasty.

METHODS

Leukocyte count at admission and within 24h after angioplasty, and differential count at admission were obtained in 72 consecutive patients with a first AMI (mean age 56±12 years) successfully treated by primary angioplasty. Transthoracic Doppler echocardiography was performed within 24h after angioplasty and 3 months later to assess the CFR (using intravenous adenosine), in the left anterior descending artery (LAD), left ventricular ejection fraction (LVEF) and the wall motion score index using the nine segments assigned to the LAD territory (WMSi-lad). In hospital events were defined as death, heart failure (Killip≥2) and reinfarction.

RESULTS

Leukocyte count was higher before and after angioplasty in patients with impaired acute CFR (<1.7), when compared to patients without such impairment (P≤0.01), and a significant correlation was found between CFR and leukocyte, neutrophil and monocyte count (P<0.05). Leukocyte (before and after angioplasty), and neutrophil count, were lower in patients with recovery of global and regional LV function (P<0.05). A significant correlation was found between leukocyte count before and after angioplasty, and, initial and follow-up LVEF, and WMSi-lad (all, P≤0.01). Leukocyte (before and after angioplasty) and monocyte count were higher in patients with in-hospital events (n=14), by comparison to patients without events (all, P<0.01). In multivariate analysis, leukocyte count after angioplasty was an independent predictor of CFR, and in-hospital events, and neutrophil count of WMSi-lad at follow-up (all, P<0.05).

CONCLUSION

In the first AMI treated successfully by primary angioplasty, leukocyte count is inversely correlated to CFR, and global and regional LV systolic function at follow-up. These links are higher after than before reperfusion. And, leukocyte count after angioplasty is an independent predictor of in-hospital adverse events.

Condensed mitotic chromosome structure at nanometer resolution using PALM and EGFP- histones

Photoactivated localization microscopy (PALM) and related fluorescent biological imaging methods are capable of providing very high spatial resolutions (up to 20 nm). Two major demands limit its widespread use on biological samples: requirements for photoactivatable/photoconvertible fluorescent molecules, which are sometimes difficult to incorporate, and high background signals from autofluorescence or fluorophores in adjacent focal planes in three-dimensional imaging which reduces PALM resolution significantly. We present here a high-resolution PALM method utilizing conventional EGFP as the photoconvertible fluorophore, improved algorithms to deal with high levels of biological background noise, and apply this to imaging higher order chromatin structure. We found that the emission wavelength of EGFP is efficiently converted from green to red when exposed to blue light in the presence of reduced riboflavin. The photon yield of red-converted EGFP using riboflavin is comparable to other bright photoconvertible fluorescent proteins that allow <20 nm resolution. We further found that image pre-processing using a combination of denoising and deconvolution of the raw PALM images substantially improved the spatial resolution of the reconstruction from noisy images. Performing PALM on Drosophila mitotic chromosomes labeled with H2AvD-EGFP, a histone H2A variant, revealed filamentous components of ∼70 nm. This is the first observation of fine chromatin filaments specific for one histone variant at a resolution approximating that of conventional electron microscope images (10-30 nm). As demonstrated by modeling and experiments on a challenging specimen, the techniques described here facilitate super-resolution fluorescent imaging with common biological samples.

Monitoring of grizzly bear population trends and demography using DNA mark–recapture methods in the Owikeno Lake area of British Columbia

We used DNA sampling and mark–recapture modeling to estimate population trend(s), population size, and the demographic response of a coastal British Columbia grizzly bear population (Ursus arctos L., 1758) to low salmon escapement levels from 1998 to 2002. We contrasted the demography of three sampling areas in response to temporal and spatial variation in salmon availability. Population trend (λ) estimates suggested that salmon availability was too low in the first 2 years of the study to sustain grizzly bear populations. One of the sampling areas exhibited higher levels of salmon availability in later years of the study, leading to increased rates of addition. Apparent survival rates increased in all areas potentially as a result of increased salmon availability. Joint interpretation of λ and superpopulation estimates allowed for the assessment of whether salmon availability levels were high enough to sustain current population sizes of grizzly bears on salmon streams. This study illustrates how joint modeling of separate sampling areas can be used to assess spatial variation in population demography and population trends, as well as increase precision of estimates for individual sampling areas. It also illustrates how DNA mark–recapture can be used as a methodology to explore the effects of changes in environmental conditions on population demography and population trend of grizzly bears or of other wildlife species.

The RNase III family: a conserved structure and expanding functions in eukaryotic dsRNA metabolism

The last few years have witnessed the appreciation of dsRNA as a regulator of gene expression, a potential antiviral agent, and a tumor suppressor. However, in spite of these clear effects on the cell function, the mechanism that controls dsRNA maturation and stability remains unknown. Recently, the discovery of eukaryotic orthologues of the bacterial dsRNA specific ribonuclease III (RNase III) suggested a central role for these enzymes in the regulation of dsRNA and eukaryotic RNA metabolism in general. This article reviews the structure-function features of the eukaryotic RNase III family and their roles in dsRNA metabolism with an emphasis on the yeast RNase III. Yeast RNase III is involved in the maturation of the majority of snRNAs, snoRNAs, and rRNA. In addition, perturbation of the expression level of yeast RNase III alters meiosis and causes sterility. These basic functions of the yeast RNase III appear to be widely conserved which makes it a good model to understand the importance of eukaryotic dsRNA metabolism.

Pulmonary effects of short-term exposure to low levels of toluene diisocyanate in asymptomatic subjects

Isocyanates may be involved in the development of chronic obstructive airway disease among exposed workers. A short-term exposure to toluene diisocyanate (TDI) at concentrations near the permissible levels was investigated to examine whether there was an association with changes in pulmonary function tests and in potential markers of airway injury and inflammation in bronchial lavage (BL) and bronchoalveolar lavage (BAL). Seventeen subjects without respiratory symptoms (eight smokers and nine nonsmokers) were exposed once to ambient air and once to TDI (5 parts per billion (ppb) for 6 h followed by 20 ppb for 20 min) in a randomized, single-blind sequence. Pulmonary function tests were repeatedly assessed during exposure and BAL was performed 1 h after each exposure. Biochemical studies on lavage fluids included albumin, immunoglobulins, antiproteases (alpha2-macroglobulin and alpha1-proteinase inhibitor), potential indicators of epithelial cell function (secretory component and Clara cell protein), and cytokines (tumour necrosis factor-alpha, interleukin (IL)-4, IL-5, IL-6, and IL-8). Exposure to TDI caused a modest decrease in specific airway conductance (sGaw) (p=0.053) and in maximal expiratory flow at 25% of forced vital capacity (MEF25%) (p=0.015) when compared with ambient air. Exposure to TDI resulted in a slight increase in BAL albumin level (TDI: 26.4+/-12.5 versus air: 21.8+/-8.6 microg x mL(-1), p=0.044) and in BL alpha2-macroglobulin concentration (TDI: 0.07+/-0.061 versus air: 0.05+/-0.04 microg x mL(-1), p=0.021). This study suggests that exposure to low toluene disocyanate concentrations is associated with minimal but detectable changes in airway calibre and in epithelial barrier permeability. The pulmonary effects of long-term exposure to low levels of isocyanates require further investigation.

Immunological and biological properties of recombinant Lol p 1

BACKGROUND

Current forms of allergy diagnosis and therapies are based on the use of natural allergenic extracts. Despite strong evidence that higher therapeutic efficacy may be achieved with purified allergens, the purification of multiple allergic components from extracts is a fastidious and sometimes an impossible task. However, the use of recombinant allergens may be an alternative to overcome this problem.

OBJECTIVE

In this study, we compared the immunological properties of recombinant (r) Lol p 1 with those of the natural protein.

METHOD

We cloned directly the gene encoding Lol p 1 from genomic DNA of ryegrass pollen. This gene was subcloned into the expression vector pMAL-c and expressed as fusion protein. Subsequently, rLol p 1 was cleaved from maltose-binding protein using factor Xa. Using binding inhibition and proliferative assays, we assessed the immunological properties of the recombinant allergens. The capacity of rLol p 1 to trigger basophil histamine release and to elicit a skin reaction was also assessed and compared to those of its natural counterpart.

RESULTS

We found that the Lol p 1 gene has no introns since we amplified this gene directly from genomic DNA. We demonstrated that the binding sites of anti-Lol p 1 monoclonal antibody, specific human IgG and IgE antibody are well conserved on rLol p 1 as no difference in the binding inhibition profile was observed when using either natural or recombinant protein. At the T-cell level, rLol p 1 elicited a T-cell response in mice comparable to that observed with the natural protein. In addition, we demonstrated that the biological characteristics of rLol p 1 were comparable to those of the natural counterpart, in that rLol p 1 elicited a skin wheal reaction and induced basophil histamine release in grass-allergic patients only.

CONCLUSION

The data indicate that natural Lol p 1 and rLol p 1 shared identical immunological and biological properties.

[Cervical dysplasia: is there a role for hysterectomy?]

Cervical intraepithelial neoplasia are usually treated by conservative procedures. Hysterectomy straightaway would have advantages but some drawbacks; reasons are listed.

[Pulmonary hypertension associated with portal hypertension. Apropos of 2 cases]

The authors report the cases of two patients with pulmonary hypertension associated with portal hypertension. This is a rare association with a reported prevalence ranging from 0.25 to 0.73%. The diagnosis of portal hypertension preceded that of pulmonary hypertension by several years. The physiopathological mechanism of the latter is not well known although several hypotheses have been proposed. Treatment is only symptomatic. The prognosis is usually poor, the causes of death being related to complications of liver failure and/or portal hypertension or to those of pulmonary hypertension.

Members of the 70 kDa heat shock protein family specifically recognize sulfoglycolipids: role in gamete recognition and mycoplasma-related infertility

We have previously shown that several mycoplasma species associated with infertility bind specifically to sulfated glycolipids isolated from the mammalian reproductive tract. We now show that a germ cell-specific sulfoglycolipid binding protein (SLIP 1), which is a potent inhibitor of sperm/egg binding in vitro, is immunologically related to the heat shock protein(Hsp) 70 family of stress proteins and that Hsps are surface antigens in male germ cells. Our present data demonstrate that several mycoplasma and mammalian Hsps share this glycolipid binding specificity in vitro, and suggest that surface Hsps can function as adhesins which mediate sulfoglycolipid recognition in infectious disease and normal reproductive physiology.

Mediation of glucocorticoid receptor function by the activation of latent transforming growth factor beta 1 in MG-63 human osteosarcoma cells

We analyzed glucocorticoid receptor function using ligand binding assays, DNA band-shift analysis and trans-activation of the murine mammary tumor virus-thymidine kinase-chloramphenicol acetyltransferase reporter gene in transiently transfected MG-63 human osteosarcoma cells. Dexamethasone increased the distribution of MG-63 cells in the G1/G0 phase of the cell cycle, thus decreasing the rate of DNA synthesis and cell growth. Its effect on MG-63 cell growth was neutralized by RU486 and anti-transforming growth factor beta 1 (TGF beta 1) antibody. In addition, (i) dexamethasone increased the levels of active TGF beta 1 in MG-63-conditioned media without significantly altering the expression of TGF beta 1 mRNA in MG-63 cells and (ii) TGF beta 1 inhibited proliferation of MG-63 cells. Therefore, we conclude that glucocorticoid receptor function is mediated by the activation of latent-TGF beta 1 in MG-63 osteosarcoma cells.

Occupational asthma due to gas metal arc welding on mild steel

Occupational asthma has been documented in electric arc welders exposed to manual metal arc welding on stainless steel. A subject is described who developed late and dual asthmatic reactions after occupational-type challenge exposure to gas metal arc welding on uncoated mild steel.

Mediation of glucocorticoid receptor function by transforming growth factor beta I expression in human PC-3 prostate cancer cells

We investigated the role of glucocorticoids in controlling the proliferation of androgen-independent PC-3 human prostate cancer cells via the action of transforming growth factor beta 1 (TGF beta 1). The presence of glucocorticoid receptor (GR) in PC-3 cells was detected by immunoblotting analysis using a rabbit anti-GR polyclonal antibody against the synthetic human GR peptide (hGR383-393). In PC-3 cells, GR bound radiolabeled dexamethasone with an affinity similar to wild-type GR. In addition, GR-ligand complex bound radiolabeled DNA as detected by DNA band-shift analysis on gel electrophoresis and trans-activated the mouse mammary tumor virus-thymidine kinase-chloramphenicol acetyltransferase chimeric gene in transiently transfected PC-3 cells. Dexamethasone (0.1 up to 100 nM) and TGF beta 1 (0.5 up to 50 ng/ml) inhibited PC-3 cell proliferation. TGF beta 1 and dexamethasone both increased the distribution of PC-3 cells into the G1/G0 phase of the cell cycle. Platelet-derived growth factor (PDGF) stimulated the proliferation of PC-3 cells and overcame dexamethasone's inhibition of PC-3 cell growth. Dexamethasone's inhibition (10(-7) M) of PC-3 cell growth was completely neutralized by RU 486 (10(-6)M) and partly neutralized by anti-TGF beta 1 polyclonal antibody. Furthermore, dexamethasone up modulated the expression of TGF beta 1 mRNA in PC-3 cells. Because dexamethasone's inhibition was neutralized at least in part by an anti-TGF beta 1 polyclonal antibody and dexamethasone up modulated the expression of TGF beta 1 mRNA in PC-3 cells, we conclude that GR function in human PC-3 prostate cancer cells is mediated at least in part by TGF beta 1 expression.

Universal method for the facile production of glycolipid/lipid matrices for the affinity purification of binding ligands

Glycolipid recognition is a common motif in cellular physiology and bacterial pathogenesis. Such protein/lipid interactions are most conveniently demonstrated by the thin-layer chromatogram overlay. We have designed a simple affinity matrix for the purification of such glycolipid (or lipid) binding ligands based on the same principle, i.e., glycolipid (or lipid) adsorbed onto silica. The versatility of the procedure is demonstrated by the purification of several anti-glycolipid antibodies and anti-phosphatidyl ethanolamine (anti-PE) and the affinity purification of the Escherichia coli-derived verotoxin which binds to globotriaosyl ceramide.

Six group I introns and three internal transcribed spacers in the chloroplast large subunit ribosomal RNA gene of the green alga Chlamydomonas eugametos

The chloroplast large subunit rRNA gene of Chlamydomonas eugametos and its 5' flanking region encoding tRNA(Ile) (GAU) and tRNA(Ala) (UGC) have been sequenced. The DNA sequence data along with the results of a detailed RNA analysis disclosed two unusual features of this green algal large subunit rRNA gene: (1) the presence of six group I introns (CeLSU.1-CeLSU.6) whose insertion positions have not been described previously, and (2) the presence of three short internal transcribed spacers that are post-transcriptionally excised to yield four rRNA species of 280, 52, 810 and 1720 nucleotides, positioned in this order (5' to 3') in the primary transcript. Together, these RNA species can assume a secondary structure that is almost identical to that proposed for the 23 S rRNA of Escherichia coli. All three internal transcribed spacers map to variable regions of primary sequence and/or potential secondary structure, whereas all six introns lie within highly conserved regions. The first three introns are inserted within the sequence encoding the 810 nucleotide rRNA species and map within domain II of the large subunit rRNA structure; the remaining introns, found in the sequence encoding the 1720 nucleotide rRNA species, lie within either domain IV or V, as is the case for all other large subunit rDNA introns that have been documented to date. CeLSU.5 and CeLSU.6 each contain a long open reading frame (ORF) of more than 200 codons. While the CeLSU.6 ORF is not related to any known ORFs, the CeLSU.5 ORF belongs to a family of ORFs that have been identified in Podospora and Neurospora mitochondrial group I introns. The finding that a polymorphic marker showing unidirectional gene conversion during crosses between C. eugametos and Chlamydomonas moewusii is located within the CeLSU.5 ORF makes it likely that this intron is a mobile element and that its ORF encodes a site-specific endonuclease promoting the transfer of the intron DNA sequence.

Neutralization receptor-based immunoassay for detection of neutralizing antibodies to Escherichia coli verocytotoxin 1

The NeutRELISA, a modification of the receptor enzyme-linked immunosorbent assay developed for the detection of verocytotoxin 1 (VT1) which permits the rapid detection of neutralizing antibodies (NAb) against this toxin, has been performed. A standard concentration of VT1 was preincubated with VT-immune or nonimmune rabbit serum. The serum-toxin mixtures were then added to microtiter plates coated with deacylated globotriosyl ceramide (lyso-Gb3). The reduction of VT1 binding to lyso-Gb3 in the immune serum-toxin mixtures compared with the VT1-Gb3 binding in the nonimmune serum-toxin mixtures was detected by using mouse monoclonal antibody to VT1. After standardization of the NeutRELISA with rabbit sera, 57 human control serum samples were tested to establish a cutoff value below which NeutRELISA results would be considered positive. Thirty-three single serum samples known to demonstrate NAb to VT1 by biological assay reproducibly demonstrated VT1 NAb when tested by the NeutRELISA. There was a close correlation between the biological VT1 neutralization assay and the NeutRELISA. This assay offers a practical, rapid, and reliable approach for the detection of NAb to VT1 and other verocytotoxins.

Two group I introns with long internal open reading frames in the chloroplast psbA gene of Chlamydomonas moewusii

We report the nucleotide sequence of the chloroplast psbA gene encoding the 32 kilodalton protein of photosystem II from Chlamydomonas moewusii. Like its land plant homologues, this green algal protein consists of 353 amino acids. The C. moewusii psbA gene is composed of three exons containing 252, 11 and 90 codons and of two group I introns containing 2363 and 1807 nucleotides. Each of the introns features an internal open reading frame (ORF) that potentially encodes a basic protein of more than 300 residues. The primary sequences of the putative intron-encoded proteins are unrelated and none of them shares conserved elements with any of the proteins predicted from the group I intron sequences published so far. The first C. moewusii intron is inserted at the same position as the fourth intron of the psbA gene from Chlamydomonas reinhardtii; the second intron lies at a novel site downstream of this position. On the basis of their RNA secondary structures, the C. moewusii introns 1 and 2 can be assigned to subgroups IA and IB, respectively. However, intron 1 is not typical of subgroup IA introns, its most unusual feature being the location of the ORF in the "loop L5" region. To our knowledge, this is the first time that an ORF is located in this region of the group I intron structure.