Gene-environment interaction modulated by allelic heterogeneity in inflammatory diseases

CARD15 is a major susceptibility gene for a frequent multifactorial chronic inflammatory bowel disorder, Crohn disease (CD). By using NF-kappaB activation assays, the cytosolic CARD15 was shown to efficiently detect bacterial peptidoglycan (PGN), reminiscent of the PGN recognition protein surveillance mechanism in Drosophila. The 3 CD-associated variants and 13 additional variants carried by CD patients demonstrated impaired PGN-dependent response revealing null, hypomorphic, or dominant-negative properties. Quantitative parametrization of this response, computed from the patients' CARD15 genotypes, was predictive of several variable CD manifestations. In contrast, CARD15 alleles associated with Blau's syndrome promoted PGN-independent NF-kappaB activation, an observation that accounts for the minimal microbial input in the etiology of this dominant, monogenic inflammatory disorder affecting solely aseptic sites.     

Colorectal Anastomotic Stenosis After Elective Laparoscopic Sigmoidectomy for Diverticular Disease: A Prospective Evaluation of 68 Patients

Purpose  This prospective study was designed to find the incidence of symptomatic anastomotic stenosis after elective laparoscopic sigmoidectomy for diverticular disease. Methods  Sixty-eight patients who underwent elective laparoscopic sigmoidectomy with double-stapling colorectal anastomosis between November 1998 and June 2007 were included. Follow-up after hospitalization was performed by using sequential rectoscopy for all patients. Symptomatic patients with anastomotic stricture were treated. Results  No patient died postoperatively and no patient had anastomotic leak or abdominal septic complication. Twenty-two patients (32 percent) had postoperative symptoms that suggested anastomotic stenosis; 12 of them (17.6 percent) eventually needed dilatation of their anastomosis (median diameter of the stenosis: 7 mm) a mean time of 176 days postoperatively. Eight patients had only one session, three patients had two sessions, and one patient had three sessions. There were no complications and all patients were symptom-free after dilatation. Age, sex, obesity, hypertension, diabetes, and vascular preservation had no influence on the risk of anastomotic stenosis. Conclusions  Incidence of symptomatic anastomotic stenosis after elective laparoscopic sigmoidectomy is high (17.6 percent). No risk factor could be identified. Endoscopic dilatations were successful without complication in all cases. Regular rigid rectoscopy definitely should be part of the postoperative follow-up in symptomatic patients.     

Acoustic excitations and elastic heterogeneities in disordered solids

In the recent years, much attention has been devoted to the inhomogeneous nature of the mechanical response at the nanoscale in disordered solids. Clearly, the elastic heterogeneities that have been characterized in this context are expected to strongly affect the nature of the sound waves which, in contrast to the case of perfect crystals, cannot be completely rationalized in terms of phonons. Building on previous work on a toy model showing an amorphization transition, we investigate the relationship between sound waves and elastic heterogeneities in a unified framework by continuously interpolating from the perfect crystal, through increasingly defective phases, to fully developed glasses. We provide strong evidence of a direct correlation between sound wave features and the extent of the heterogeneous mechanical response at the nanoscale.In crystals, molecules thermally oscillate around the periodic lattice sites and vibrational excitations are well understood in terms of quantized plane waves, the phonons (1). The vibrational density of states (vDOS) in the low-frequency regime is well described by the Debye model, where the vibrational modes are the acoustic phonons. In contrast, disordered solids, including structural glasses and disordered crystals, exhibit specific vibrational properties compared with the corresponding pure crystalline phases. It is not possible here to give a fair review of the extensive theoretical and experimental work generated by these issues; we therefore mention below a few facts that we consider the most relevant in the present context. The origin of the vDOS modes in excess over the Debye prediction around ω ∼1 THz, the so-called Boson peak (BP), is still debated (see, among many others, refs. 2 and 3). At the BP frequency, Ω^BP, localized modes have also been observed (4). Acoustic plane waves, which are exact normal modes in crystals, can still propagate in disordered solids. Indeed, at low frequencies, Ω, and long wavelengths, Λ, acoustic sound waves do not interact with disorder and can propagate conforming to the expected macroscopic limit. However, as Ω is increased beyond the Ioffe–Regel (IR) limit, Ω^IR, acoustic excitations interact with the disorder and are significantly scattered (5–7). Interestingly, this strong scattering regime occurs around the BP position, Ω^IR ∼ Ω^BP (8, 9). The exact origin of this phenomenon and its connection to the BP remain elusive.A possible rationalization of the above issues is based on the existence of elastic heterogeneities (10), which can originate from structural disorder, as in structural glasses (2), or disordered interparticle potentials, even in lattice structures such as disordered colloidal crystals (11). In the heterogeneous-elasticity theory of refs. 7 and 12 this amounts to consider spatial statistical fluctuations of the shear modulus. Within the framework of jamming approaches and using effective medium theories, elastic heterogeneities are related to the proximity of local elastic instabilities (13). Recent simulation work (14–16) has clearly demonstrated their existence in disordered solids. This is at variance with the case of simple crystals, which are characterized by a fully affine response and homogeneous moduli distributions (17). More specifically, in the large length scale limit, macroscopic moduli are observed. In contrast, as the length scale is reduced, moduli heterogeneities are detected, at a typical length scale ξ ≃ 10−15σ (15), where σ is the typical atomic diameter. Breakdown of both continuum mechanics (18) and Debye approximation (5, 6) has been demonstrated at the same mesoscopic length-scale ξ, where they are still valid for crystals. Remarkably, the wave frequency corresponding to the wavelength Λ ∼ ξ is very close to Ω^IR ∼ Ω^BP (19). Altogether these results indicate that a close connection must exist between elastic heterogeneities and acoustic excitations. In this paper we precisely address this point.In ref. 20 we considered a numerical model featuring an amorphization transition (21). We showed how to systematically deform the local moduli distributions, evaluated by coarse-graining the system in small domains of linear length scale w. We characterized the degree of elastic heterogeneity in terms of SD of those distributions and studied the effect on normal modes (eigenvalues of the Hessian matrix) and thermal conductivity. Building on that work, we are now in the position to investigate the relation between elastic heterogeneities and acoustic excitations, unifying in a single framework ordered and disordered solid states and considering quantities directly probed by experiments. By interpolating in a controlled way from perfect crystals, through increasingly defective phases, to fully developed amorphous structures, we (i) calculate the dynamical structure factors, extracting the relevant spectroscopic parameters; (ii) characterize the wave vector dependence of sound velocity and broadening of the acoustic excitations and clarify their nature in terms of the IR limit; and (iii) provide, for the first time to our knowledge, direct evidence of the correlation of the excitations lifetimes and Ω^IR with the magnitude of the elastic heterogeneities.     

Family study of lipoprotein lipase gene polymorphisms and plasma triglyceride levels

To better characterize the role of the lipoprotein lipase (LPL) gene in the determination of triglyceride levels in healthy subjects, a study was performed in 193 nuclear families (384 parents, means age = 42.0 ± 5.2 years; 399 offspring, mean age = 14.6 ± 4.3 years) volunteering to have a free health checkup examination. The pattern of familial resemblance was compatible with a zero correlation between spouses, a weak father-offspring correlation (0.099 ± 0.054; P < 0.07), and significant mother-offspring (0.235 ± 0.053; P < 10⁻⁴) and sib-sib (0.294 ± 0.064; P < 10⁻⁴) correlations. Associations of triglyceride levels with the LPL HindIII and PvuII polymorphisms were investigated by a familial measured genotype analysis, specifying sex- and age-dependent polymorphism effects. The effects associated with both polymorphisms were significant only in fathers, the H+ and P+ alleles being associated with raised triglyceride levels. The HindIII and PvuII polymorphisms explained 3.5% and 3%, respectively, of the variability of triglycerides in fathers. The relationship was weakened after prior adjustment on body mass index, but remained significant for PvuII. Because of the lack of effect in mothers and offspring, the polymorphisms did not contribute to the covariance of triglyceride levels in relatives. In conclusion, this family study showed a weak relationship of the HindIII and PvuII polymorphisms to plasma triglyceride levels in young healthy male subjects. The effects detectable only in fathers suggest a possible modulation of the LPL expression by hormonal or lifestyle factors. © 1996 Wiley-Liss, Inc.     

Ciliary melanin-concentrating hormone receptor 1 (MCHR1) is widely distributed in the murine CNS in a sex-independent manner

Melanin-concentrating hormone (MCH) is a ubiquitous vertebrate neuropeptide predominantly synthesized by neurons of the diencephalon that can act through two G protein-coupled receptors, called MCHR1 and MCHR2. The expression of Mchr1 has been investigated in both rats and mice, but its synthesis remains poorly described. After identifying an antibody that detects MCHR1 with high specificity, we employed immunohistochemistry to map the distribution of MCHR1 in the CNS of rats and mice. Multiple neurochemical markers were also employed to characterize some of the neuronal populations that synthesize MCHR1. Our results show that MCHR1 is abundantly found in a subcellular structure called the primary cilium, which has been associated, among other functions, with the detection of free neurochemical messengers present in the extracellular space. Ciliary MCHR1 was found in a wide range of areas, including the olfactory bulb, cortical mantle, striatum, hippocampal formation, amygdala, midline thalamic nuclei, periventricular hypothalamic nuclei, midbrain areas, and in the spinal cord. No differences were observed between male and female mice, and interspecies differences were found in the caudate-putamen nucleus and the subgranular zone. Ciliary MCHR1 was found in close association with several neurochemical markers, including tyrosine hydroxylase, calretinin, kisspeptin, estrogen receptor, oxytocin, vasopressin, and corticotropin-releasing factor. Given the role of neuronal primary cilia in sensing free neurochemical messengers in the extracellular fluid, the widespread distribution of ciliary MCHR1, and the diverse neurochemical populations who synthesize MCHR1, our data indicate that nonsynaptic communication plays a prominent role in the normal function of the MCH system.     

Analytical Sensitivity of Six SARS-CoV-2 Rapid Antigen Tests for Omicron versus Delta Variant

Rapid antigen detection (RAD) tests are commonly used for the diagnosis of SARS-CoV-2 infections. However, with the continuous emergence of new variants of concern (VOC), presenting various mutations potentially affecting the nucleocapsid protein, the analytical performances of these assays should be frequently reevaluated. One hundred and twenty samples were selected and tested with both RT-qPCR and six commercial RAD tests that are commonly sold in Belgian pharmacies. Of these, direct whole-genome sequencing identified the strains present in 116 samples, of which 70 were Delta and 46 were Omicron (BA.1 and BA.1.1 sub-lineages, respectively). The sensitivity across a wide range of Ct values (13.5 to 35.7; median = 21.3) ranged from 70.0% to 92.9% for Delta strains and from 69.6% to 78.3% for Omicron strains. When taking swabs with a low viral load (Ct > 25, corresponding to <4.9 log₁₀ copies/mL), only the Roche RAD test showed acceptable performances for the Delta strains (80.0%), while poor performances were observed for the other RAD tests (20.0% to 40.0%). All the tested devices had poor performances for the Omicron samples with a low viral load (0.0% to 23.1%). The poor performances observed with low viral loads, particularly for the Omicron strain, is an important limitation of RAD tests, which is not sufficiently highlighted in the instructions for use of these devices.     

Ghrelin receptor conformational dynamics regulate the transition from a preassembled to an active receptor:Gq complex

How G protein-coupled receptor conformational dynamics control G protein coupling to trigger signaling is a key but still open question. We addressed this question with a model system composed of the purified ghrelin receptor assembled into lipid discs. Combining receptor labeling through genetic incorporation of unnatural amino acids, lanthanide resonance energy transfer, and normal mode analyses, we directly demonstrate the occurrence of two distinct receptor:Gq assemblies with different geometries whose relative populations parallel the activation state of the receptor. The first of these assemblies is a preassembled complex with the receptor in its basal conformation. This complex is specific of Gq and is not observed with Gi. The second one is an active assembly in which the receptor in its active conformation triggers G protein activation. The active complex is present even in the absence of agonist, in a direct relationship with the high constitutive activity of the ghrelin receptor. These data provide direct evidence of a mechanism for ghrelin receptor-mediated Gq signaling in which transition of the receptor from an inactive to an active conformation is accompanied by a rearrangement of a preassembled receptor:G protein complex, ultimately leading to G protein activation and signaling.G protein-coupled receptors (GPCRs), one of the largest cell surface receptor families, are involved in many cellular signaling processes (1). Based on this property, as well as their importance as drug targets, the molecular aspects of GPCR functioning have been extensively investigated. In particular, coupling to heterotrimeric G proteins has been the focus of numerous studies. Indeed, delineating the molecular mechanisms responsible for receptor:G protein interaction is absolutely required to better understand how signaling is controlled. Recent years have seen spectacular advances that have culminated in elucidation of the 3D structure of the β₂-adrenergic receptor:Gs complex (2). Nevertheless, the need for further progress remains, in particular to fully understand the dynamics of this interaction. This is a crucial question, given that how the receptor interacts with its G protein partner governs signaling, and thus biological and pathophysiological responses.To date, two different models for GPCR:G protein interaction have been proposed: collision coupling and preassembly. Originally, it was proposed that receptors and G proteins couple by collision (3, 4). One of the main features of this model is that only activated receptors interact with G proteins. Since then, alternative models of signaling have been developed. One of these, the preassembly model, proposes that the receptor and the G protein make a complex even in the absence of agonist (5–8). Discriminating between the two models is crucial. Indeed, signaling outputs, such as the kinetics of G protein activation, will be significantly different depending on whether the ligand-free receptor is always in complex with its G protein or must first be activated by the agonist to recruit the G protein and trigger signaling. Moreover, it has been shown that GPCR conformational dynamics (9–11) and signaling in the absence of ligand are key features of GPCR functioning (12). How receptor constitutive activity and conformational dynamics relate to their coupling to the G protein remains an open question.Here we used the purified ghrelin receptor GHS-R1a to analyze the way in which this GPCR interacts with its G protein partners. Ghrelin is a neuroendocrine peptide hormone that acts through its cognate GPCR to control important biological processes, such as growth hormone secretion, food intake, and reward-seeking behaviors (13). Among the GPCRs, GHS-R1a has been shown to have one of the highest basal Gq activation levels both in vitro (10, 14) and in vivo (15, 16). The physiological relevance of GHS-R1a basal activity is substantiated by the occurrence of a natural human mutation in the GHS-R1a gene (A²⁰⁴E substitution in the second extracellular loop of the receptor) that dramatically decreases constitutive activity and is associated with a short-stature phenotype (17). Along with its importance in drug design, GHS-R1a is a prototype for peptide-activated class A GPCRs.To delineate the way in which the ghrelin receptor interacts with G proteins, we used monomeric GHS-R1a reconstituted in a membrane-mimicking environment, lipid discs, and a combination of innovative biochemical [labeling with unnatural amino acid (UAA)] and biophysical [lanthanide resonance energy transfer (LRET) and normal mode (NM) analyses] approaches. By doing so, we provide the first direct evidence that ghrelin-mediated signaling involves a complex dialogue between the conformational dynamics of the receptor and its ability to interact with the different G protein subtypes to which it is coupled.     

Follicular dendritic cell tumor of the mediastinum: expression of fractalkine and SDF-1α as mast cell chemoattractants

Follicular dendritic cell tumor (FDCT) is a rare tumor mainly located in laterocervical lymph nodes. We report one case of mediastinal FDCT associated with a history of bullous skin disease and clinically obvious immunosuppression. This tumor was characterized by heavy mast cell infiltration. Mast cells were in close relationship with tumor cells as demonstrated by ultrastructural examination and their presence are probably related with the strong expression of mast cell chemoattractants as fraktalkine and stromal cell-derived factor-1α by tumor cells. The long follow-up period of more than 17 years allowed to us assess the relatively indolent evolution of this tumor characterized by three slowly growing local recurrences without metastasis.     

Hyponatremia in neurological patients: cerebral salt wasting versus inappropriate antidiuretic hormone secretion

Objective To assess whether hyponatremia in acute neurological patients is associated with the syndrome of inappropriate antidiuretic hormone secretion (SIADH) or with the cerebral salt-wasting syndrome (CSWS). Design Clinical, controlled, prospective study. Setting Department of intensive care of a tertiary care academic hospital. Patients Forty acute neurological patients with hyponatremia suggesting SIADH or CSWS (20) or with normonatremia (20). Interventions None. Measurements and main results Measurement of clinical and biological variables. Measurement of blood, plasma, and red blood cell volumes to discriminate SIADH and CSWS. Renal, adrenal and thyroid functions were normal in all patients. Average blood, plasma, and red blood cell volumes were 54, 37 and 17 ml/kg in control patients and 54, 37 and 18 ml/kg in hyponatremic patients, respectively. Conclusions The adequate blood volumes in hyponatremic patients confirm the diagnosis of SIADH and do not support the concept of CSWS. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.