Measurement of left mainstem bronchus using multiplane CT reconstructions and relationship between patient characteristics or tracheal diameters and left bronchial diameters

STUDY OBJECTIVES: To measure the tracheal diameters (TDs) [transverse (Tr) TD, and anteroposterior (AP) TD] and left main bronchus diameters (LBDs) [Tr and AP] using multiplane CT scan reconstructions with a tridimensional correction of the declination. To evaluate the relationship between clinical variables and CT scan diameters of the tracheobronchial tree. To aid in the selection of a double-lumen tube of appropriate size. DESIGN: Prospective observational study. SETTING: Private and university hospitals. PATIENTS: A total of 206 patients (105 women and 101 men) undergoing a CT scan for medical investigations or preoperative evaluation. INTERVENTION: No intervention. MEASUREMENTS AND RESULTS: TDs and LBDs are greater in men (p < 0.001). The Tr-TD is smaller than AP-TD for men (p < 0.001). The Tr-LBD is greater than AP-LBD in both sexes (p < 0.001). In men, height, Tr-TD, and AP-TD are predictive factors for Tr-LBD, while Tr-TD and AP-TD are the only predictive factors for AP-LBD. In women, Tr-TD and AP-TD are the only predictive factors for Tr-LBD and AP-LBD. The smallest LBD (ie, the lesser of the Tr-LBD or the AP-LBD [called the smallest LBD]) is the Tr-LBD in 25.2% of the cases. The mean (+/- SD) ratio of the smallest LBD/Tr-TD is 0.70 +/- 0.14 for men and 0.65 +/- 0.12 for women. The estimated (Est) LBD is calculated using this ratio. The mean value for Est-LBD minus the smallest LBD is 1.6 +/- 1.3 mm, and this difference is < 1 mm in 40% of male patients and 39% of female patients. CONCLUSIONS: In conclusion, the left main bronchus is most often elliptic, and the smallest LBD cannot be accurately evaluated using patient characteristics or a ratio from TD.     

From the Cover: FtsK translocation permits discrimination between an endogenous and an imported Xer/dif recombination complex

In bacteria, the FtsK/Xer/dif (chromosome dimer resolution site) system is essential for faithful vertical genetic transmission, ensuring the resolution of chromosome dimers during their segregation to daughter cells. This system is also targeted by mobile genetic elements that integrate into chromosomal dif sites. A central question is thus how Xer/dif recombination is tuned to both act in chromosome segregation and stably maintain mobile elements. To explore this question, we focused on pathogenic Neisseria species harboring a genomic island in their dif sites. We show that the FtsK DNA translocase acts differentially at the recombination sites flanking the genomic island. It stops at one Xer/dif complex, activating recombination, but it does not stop on the other site, thus dismantling it. FtsK translocation thus permits cis discrimination between an endogenous and an imported Xer/dif recombination complex.In all organisms, the processing of chromosome ends or termini relies on specific activities for replication and segregation. In eukaryotes, telomeres are often targeted by mobile genetic elements, which may even substitute for telomeric functions (1). Circular chromosomes found in prokaryotes have no telomeres but harbor chromosome dimer resolution sites, called dif sites, on which dedicated Xer recombinases (XerC and XerD in most cases) act (2, 3). Besides their role in chromosome maintenance, dif sites are targeted by numerous mobile genetic elements, referred to as integrating mobile element exploiting Xer (IMEX) (4). How IMEXs integrate into dif without inactivating its cellular function and how they are stably maintained in their integrated state has remained unclear despite study over the past decade (4–7). Here we answer these questions by studying the gonococcal genomic island (GGI), an IMEX stably integrated into the dif site of pathogenic Neisseria species that encodes crucial functions for gene exchange and virulence (8, 9).In Escherichia coli, chromosome dimers form by homologous recombination during replication and are resolved by site-specific recombination between sister dif sites catalyzed by the XerC and XerD recombinases (Fig. 1) (3). The 28-bp dif site carries binding sites for each recombinase, separated by a 6-bp central region at the border of which strand exchanges are catalyzed. After assembly of the recombination complex (synapse), one pair of strands is exchanged by the XerD monomers, leading to a branched DNA intermediate (Holliday junction, HJ) subsequently resolved by XerC. Dimer resolution is integrated into the general processing of the terminal region of the chromosome (ter region) during cell division (10). FtsK, a DNA translocase associated with the division apparatus, segregates this region at the onset of cell division (10, 11). The translocation motor, FtsKαβ, is located in the C terminal of FtsK (12). Translocation is oriented toward the dif site located at the center of the ter region via a direct interaction between the extreme C-terminal subdomain of FtsK, FtsKγ, and the KOPS DNA motifs (13). Upon reaching the XerCD/dif complex, FtsK stops translocating and activates recombination via direct interaction with XerD (14, 15) (Fig. 1). The mechanisms of translocation arrest and of recombination activation are poorly understood but they both involve FtsKγ. However, these activities appear to be distinct from each other because FtsKγ can activate recombination in vivo and in vitro when isolated from the FtsKαβ motor or fused to XerC or XerD (16).Open in a separate windowFig. 1.The XerCD/dif recombination. (A) Chromosome dimer formation by homologous recombination (HR) during replication and resolution by site-specific recombination between the two dif sites. The dif site is represented as green and purple boxes for the XerC-binding and the XerD-binding sites, respectively. ori (black circle), some KOPS motifs (arrows), and the ter domain (thick line) are represented. The mechanism of XerCD/dif recombination is represented in the box. XerC (green circles) and XerD (purple circles) bind two distant dif sites to create a synapse. Hexamers of the FtsK C-terminal domain [FtsKC: FtsKαβ: (diamonds) + FtsKγ: (triangle) contacting XerD] translocate toward dif and contact XerD. This activates XerD (Y indicates the active recombinases), which catalyzes the first-strand exchange. This process leads to the formation of an HJ intermediate within which XerC is active and catalyzes the second-strand exchange (3). (B) Integration and excision of the GGI (dotted line) by XerCD catalysis. KOPS, dif_Ng, and dif_GGI sites are represented as in A. An alignment of dif_Ng, dif_GGI and consensus dif sequence (27, 28) is shown on the left. Substituted positions in dif_GGI are represented as lowercase characters and highlighted by stars.In numerous bacteria, the XerCD/dif system is hijacked by IMEXs, which integrate their host genome into dif sites by using XerCD-mediated catalysis (4). In all of the reported cases, integration of IMEXs recreates a bona fide dif site, thereby not interfering with chromosome dimer resolution, which would lead to their counter-selection. The best-described examples are Vibrio cholerae IMEXs, which carry crucial virulence determinants (5–7, 17). These IMEXs have developed different strategies to integrate and to remain stably integrated, although the mechanisms ensuring their stable maintenance are not fully understood. Neisseria species contain an unusually long IMEX called the gonococcal genomic island (GGI) (8). In Neisseria gonorrheae, the GGI is 57 kb long and encodes a type IV secretion system that exports the chromosomal DNA of its host, rendering it available to neighboring cells for gene exchange by genetic transformation (8, 18). The GGI carries a dif site, dif_GGI, consisting of a XerC-binding site, a central region homologous to the Neisseria dif site, dif_Ng, and a divergent XerD-binding site (Fig. 1B). Comparison of N. gonorrheae strains harboring or lacking the GGI, together with functional data, indicates that the GGI integrates by XerCD-dependent recombination (9). The nonreplicative excised circular form of the GGI can be detected and the GGI can also be lost, showing that excision occurs, although at low frequencies (9). Although the GGI was identified over a decade ago, it has remained unclear how DNA flanked by two Xer recombination sites is stably maintained at a chromosomal locus processed by FtsK during each cell cycle. In this study, we have combined in vitro and in vivo approaches to show that dif_GGI is indeed an active Xer recombination site at which the Neisseria Xer recombinases catalyze recombination when activated by FtsKγ. However, we find that recombination between dif_Ng and dif_GGI is inhibited by translocating FtsK. Inhibition is a result of the absence of translocation arrest at XerCD_Ng/dif_GGI complexes that most likely precludes recombination activation, an absence that causes the complex to dismantle. We conclude that, depending on the sequence of the recombination site, Xer recombination complexes have the intrinsic capacity to be activated or inhibited by FtsK.     

Tissue fusion over nonadhering surfaces

Tissue fusion eliminates physical voids in a tissue to form a continuous structure and is central to many processes in development and repair. Fusion events in vivo, particularly in embryonic development, often involve the purse-string contraction of a pluricellular actomyosin cable at the free edge. However, in vitro, adhesion of the cells to their substrate favors a closure mechanism mediated by lamellipodial protrusions, which has prevented a systematic study of the purse-string mechanism. Here, we show that monolayers can cover well-controlled mesoscopic nonadherent areas much larger than a cell size by purse-string closure and that active epithelial fluctuations are required for this process. We have formulated a simple stochastic model that includes purse-string contractility, tissue fluctuations, and effective friction to qualitatively and quantitatively account for the dynamics of closure. Our data suggest that, in vivo, tissue fusion adapts to the local environment by coordinating lamellipodial protrusions and purse-string contractions.Tissue fusion is a frequent and important event during which two facing identical tissues meet and bridge collectively over a gap before merging into a continuous structure (1). Imperfect tissue fusion in embryonic development results in congenital defects for instance, in the palate, the neural tube, or the heart (1). Epithelial wound healing is another illustration of tissue fusion through which a gap in an epithelium closes to restore the integrity of the monolayer (2).Model in vitro experiments have been developed using cell monolayers to study the different stages of healing from collective cell migration to the final stages of closure. In this context, we (3) and others (4, 5) have recently demonstrated that, for cells adhering to their substrate, and despite the presence of a contractile peripheral actomyosin cable at the free edge, the final stages of closure of wounds larger than a typical cell size result mostly from protrusive lamellipodial activity at the border. In that case, the function of the actin cable appears to be primarily to prevent the onset of migration fingers led by leader cells (6) at the free edge. Cell crawling has also been shown to have a major role in tissue fusion in vivo, for example during the closure of epithelial wounds in the Drosophila embryo (7).However, in physiological developmental situations, there is often no underlying substrate to which lamellipodia can adhere to exert traction forces. This is the case, for instance, in neural tube formation (8) or in wound healing in the Xenopus oocyte (9). The generally well-accepted mechanism in these adhesion-free situations is the so-called purse-string mechanism in which the actomyosin cable at the edge of the aperture closes it by contractile activity (10). Note that the purse-string and the crawling mechanisms are not mutually exclusive (11) and may be involved at different stages of the closure (5, 12). In addition, “suspended” cohorts of cells, which do not interact with a substrate besides being anchored to a few discrete attachment points, are also observed in situations such as collective migration in cancer invasion (13).Several experimental studies have documented protrusion-driven collective migration in vitro, but the purse-string mechanism has not been thoroughly investigated in model situations. Such an analysis imposes to suppress the contribution of the protrusions to closure and, therefore, to conduct the experiments on nonadherent substrates.In a seminal paper, fibroblast sheets were shown to grow and migrate with their sides anchored to thin glass fibers (14). More recent studies extended this observation to keratinocyte monolayers or epidermal stem cells bridging between microcontact-printed adhesive tracks (15, 16). However, despite recent advances emphasizing the role of tissue remodeling (17), the mechanism of closure of a suspended epithelium in the absence of these anchoring sites remains an open question. To address this point, we have studied the dynamics of gap closure in an unsupported epithelium in which the actomyosin cable and the suspended tissue could not adhere to the substrate. Purse-string contractility in the absence of protrusions was therefore studied on well-defined mesoscopic nonadherent patches within an adherent substrate.     

Stimulus features coded by single neurons of a macaque body category selective patch

Body category-selective regions of the primate temporal cortex respond to images of bodies, but it is unclear which fragments of such images drive single neurons’ responses in these regions. Here we applied the Bubbles technique to the responses of single macaque middle superior temporal sulcus (midSTS) body patch neurons to reveal the image fragments the neurons respond to. We found that local image fragments such as extremities (limbs), curved boundaries, and parts of the torso drove the large majority of neurons. Bubbles revealed the whole body in only a few neurons. Neurons coded the features in a manner that was tolerant to translation and scale changes. Most image fragments were excitatory but for a few neurons both inhibitory and excitatory fragments (opponent coding) were present in the same image. The fragments we reveal here in the body patch with Bubbles differ from those suggested in previous studies of face-selective neurons in face patches. Together, our data indicate that the majority of body patch neurons respond to local image fragments that occur frequently, but not exclusively, in bodies, with a coding that is tolerant to translation and scale. Overall, the data suggest that the body category selectivity of the midSTS body patch depends more on the feature statistics of bodies (e.g., extensions occur more frequently in bodies) than on semantics (bodies as an abstract category).The body category-selective regions in the human occipito-temporal cortex are defined as those that respond to images of bodies (1–8). We previously identified two bilateral regions in the macaque inferotemporal cortex that respond stronger to monkey, human, and animal bodies in comparison with other stimuli, including faces (6). Subsequent single-unit recordings in the posterior body patch [i.e., the middle superior temporal sulcus (midSTS) body patch] demonstrated that indeed the average spiking activity of the neuron population was greater to images of bodies compared with other objects. However, the responses of single neurons showed a strong selectivity for particular body—and sometimes nonbody—images (7). However, it is still unknown what particular stimulus features single body patch neurons respond to. Moreover, we still do not know how those neurons code information about different animate and inanimate stimuli.The Bubbles technique (9), in which parts of the image of an object are sampled by trial-unique randomly positioned Gaussian apertures, has been used successfully in many psychophysical studies to reveal the features critical for certain perceptual tasks such as face identification, gender discrimination, emotional discrimination, and so forth (e.g., refs. 9–13). Although this technique has been used in neuroimaging [functional MRI (fMRI), EEG, magnetoencephalography (MEG), and electrocorticography] studies (11, 12, 14), it has rarely been exploited in single-unit studies (15, 16), and this only for face stimuli.Here, we used the Bubbles technique to reveal the image fragments that drive single midSTS body patch neurons. Bubbles provides an unbiased method for sampling the images with the advantage that it requires no prior specification of stimulus features to which the neurons are supposed to be selective. With fMRI, we first defined the midSTS body patch in two monkeys. Then, in this identified body patch we recorded the spiking activity of well-isolated single neurons in response to 100 images of various categories. Based on the spiking activity to the 100 images, we selected for each neuron a response-eliciting image. Then, we sampled the selected image at five different spatial scales with randomly positioned Gaussian apertures and recorded the responses of the neuron to a large number of these trial-unique Bubbles stimuli. Following the experiment, we applied reverse correlation to relate the excitatory and inhibitory neural responses to particular image fragments.Furthermore, we assessed whether the revealed image fragments tolerated changes in spatial location and size of the Bubbles stimuli or instead reflected spatially localized image regions. We showed before that many midSTS body patch neurons respond to silhouettes of bodies (17). Silhouettes isolate shape contours, removing texture and shading information. Thus, in a subset of neurons, we applied Bubbles to a silhouette version of the selected image.     

Minimal clinically important improvement and patient acceptable symptom state for subjective outcome measures in rheumatic disorders

The concepts of minimal clinically important improvement (MCII) and patient acceptable symptomatic state (PASS) could help in interpreting results of trials involving patient-reported outcomes by translating the response at the group level (change in mean scores) into more clinically meaningful information by addressing the patient level as "therapeutic success (yes/no)." The aims of the special interest group (SIG) at OMERACT 8 were to discuss specific issues concerning the MCII and PASS concepts, especially the wording of the external anchor questions used to determine the MCII and PASS estimates, and to move toward a consensus for the cutoff values to use as the MCII and PASS in the different outcome criteria. The purpose of this SIG at OMERACT 8 was to inform participants of the MCII and PASS concepts and to agree on MCII and PASS values for pain, patient global assessment, and functional impairment.     

Comparison of in vitro-specific blood tests with tuberculin skin test for diagnosis of latent tuberculosis before anti-TNF therapy

Introduction

Latent tuberculosis infection (LTBI) is detected with the tuberculin skin test (TST) before anti‐TNF therapy. We aimed to investigate in vitro blood assays with TB‐specific antigens (CFP‐10, ESAT‐6), in immune‐mediated inflammatory diseases (IMID) for LTBI screening.

Patients and methods

Sixty‐eight IMID patients with (n = 35) or without (n = 33) LTBI according to clinico‐radiographic findings or TST results (10 mm cutoff value) underwent cell proliferation assessed by thymidine incorporation and PKH‐26 dilution assays, and IFNγ‐release enzyme‐linked immunosorbent spot (ELISPOT) assays with TB‐specific antigens.

Results

In vitro blood assays gave higher positive results in patients with LTBI than without (p<0.05), with some variations between tests. Among the 13 patients with LTBI diagnosed independently of TST results, 5 had a negative TST (38.5%) and only 2 a negative blood assays result (15.4%). The 5 LTBI patients with negative TST results all had positive blood assays results. Ten patients without LTBI but with intermediate TST results (6–10 mm) had no different result than patients with TST result ⩽5 mm (p>0.3) and lower results than those with LTBI (p<0.05) on CFP‐10+ESAT‐6 ELISPOT and CFP‐10 proliferation assays.

Conclusion

Anti‐TB blood assays are beneficial for LTBI diagnosis in IMID. Compared with TST, they show a better sensitivity, as seen by positive results in 5 patients with certain LTBI and negative TST, and better specificity, as seen by negative results in most patients with intermediate TST as the only criteria of LTBI. In the absence of clinico‐radiographic findings for LTBI, blood assays could replace TST for antibiotherapy decision before anti‐TNF.TNFα blocker agents are approved for the treatment of immune‐mediated inflammatory diseases (IMID) and provide marked clinical benefit. However, they can reactivate tuberculosis (TB) infection in patients previously exposed to TB bacilli.^1,2 The presence of quiescent mycobacteria defines latent TB infection (LTBI).^3,4 Thus, screening for LTBI is necessary before initiating therapy with TNF blockers.⁵ However, to date, no perfect gold standard exists for detecting LTBI, and tuberculin skin test (TST) remains largely used. The recommendations for detecting LTBI differ worldwide.^3,6,7 In France, recommendations were established in 2002 by the RATIO (Research Axed on Tolerance of Biotherapies) study group for the Agence Française de Sécurité Sanitaire des Produits de Santé.^8,9 Patients are considered to have LTBI requiring treatment with prophylactic antibiotics before starting anti‐TNFα therapy if they had previous TB with no adequate treatment, tuberculosis primo‐infection, residual nodular tuberculous lesions larger than 1 cm³ or old lesions suggesting TB diagnosis (parenchymatous abnormalities or pleural thickening) as seen on chest radiography or weals larger than 10 mm in diameter in response to the TST. Adequate anti‐TB treatment was defined as treatment initiated after 1970, lasting at least 6 months and including at least 2 months with the combination rifampicin–pyrazinamide. The choice of the threshold of 10 mm for the TST result was established in 2002 in France since the programme of vaccination with bacille Calmette–Guérin (BCG) was mandated in France, and nearly 100% of the population has been vaccinated. Nevertheless, after July 2005, the threshold was decreased to 5 mm as in most of all other countries.¹⁰The TST is the current method to detect LTBI but has numerous drawbacks. Indeed, the TST requires a return visit for reading the test result. It has a poor specificity, since previous BCG vaccination and environmental mycobacterial exposure can result in false‐positive results in all subjects.^6,11,12 This poor specificity can lead to unnecessary treatment with antibiotics, with a significant risk of drug toxicity.^13,14,15 On the other hand, TST in IMID may often give a more negative reaction than in the general population, mainly because of the disease or immunosuppressive drug use.^16,17 This poor sensitivity can lead to false‐negative results, with a subsequent risk of TB reactivation with anti‐TNF therapy.The identification of genes in the mycobacterium TB genome that are absent in BCG and most environmental mycobacteria offers an opportunity to develop more specific tests to investigate Mycobacterium tuberculosis (M. tuberculosis) infection, particularly LTBI.¹⁸ Culture fibrate protein‐10 (CFP‐10) and early secretory antigen target‐6 (ESAT‐6) are two such gene products that are strong targets of the cellular immune response in TB patients. In vivo‐specific T‐cell based assay investigating interferon gamma (IFNγ) release or T‐cell proliferation in the presence of these specific mycobacterial antigens could be useful in screening for LTBI before anti‐TNF therapy. New IFNγ‐based ex vivo assays involving CFP‐10 and ESAT‐6 (T‐SPOT TB, Oxford Immunotec, Abingdon, UK) and QuantiFERON TB Gold (QFT‐G; Cellestis, Carnegie, Australia) allow for diagnosis of active TB, recent primo‐infection or LTBI.¹² These tests seem to be more accurate than the TST for this purpose in the general population.¹² To date, the performance of the commercial assays in detecting LTBI in patients with IMID receiving immunosuppressive drugs has not been demonstrated, and the frequency of indeterminate results is still debated.^19,20,21We aimed to investigate the performance of homemade anti‐CFP‐10 and anti‐ESAT‐6 proliferative and enzyme‐linked immunosorbent spot (ELISPOT) assays in detecting LTBI in patients with IMID before anti‐TNFα therapy. We analysed two subgroups of patients: those with confirmed LTBI independent of TST result, and those with LTBI based exclusively on a positive TST result between 6 and 10 mm.