Rhodopsin is the only G protein-coupled receptor (GPCR) whose 3D structure is known; therefore, it serves as a prototype for studies of the GPCR family of proteins. Rhodopsin dysfunction has been linked to misfolding, caused by chemical modifications that affect the naturally occurring disulfide bond between C110 and C187. Here, we identify the structural elements that stabilize rhodopsin by computational analysis of the rhodopsin structure and comparison with data from previous in vitro mutational studies. We simulate the thermal unfolding of rhodopsin by breaking the native-state hydrogen bonds sequentially in the order of their relative strength, using the recently developed Residues most stable under thermal denaturation are part of a core, which is assumed to be important for the formation and stability of folded rhodopsin. This core includes the C110OC187 disulfide bond at the center of residues forming the interface between the transmembrane and the extracellular domains near the retinal binding pocket. Fast mode analysis of rhodopsin using the Gaussian network model also identifies the disulfide bond and the retinal ligand binding pocket to be the most rigid region in rhodopsin. Experiments confirm that 90% of the amino acids predicted by the FIRST method to be part of the core cause misfolding upon mutation. The observed high degree of conservation (78.9%) of this disulfide bond across all GPCR classes suggests that it is critical for the stability and function of GPCRs.network models ͉ membrane protein ͉ folding ͉ G protein-coupled receptor ͉ simulation R hodopsin is the only member of the G protein-coupled receptors (GPCRs), the largest family of cell-surface receptors, whose 3D structure is known (1). The signature motif of the GPCR family is a bundle of seven-transmembrane (TM) helices connected by polypeptide loops that form the cytoplasmic (CP) and the extracellular (EC) domains on opposite sides of the TM domain (Fig. 1). GPCRs perform extremely diverse and vital functions that include responses to light, odor, taste, neurotransmitters, hormones, and a variety of other signals (2). Whereas, in rhodopsin and related visual pigments, the ligand 11-cisretinal (RET) is covalently bound to the apoproteins (opsins), all other GPCRs occur in the ligand-free form, and subsequent binding of appropriate ligand(s) results in their activation. There is a wide variation in the nature of the ligands and their binding modes such as direct binding to the TM domain, the EC domain, or both.Based on pharmacological specificity and sequence conservation, GPCRs are divided into eight classes (3). Although there is no sequence homology between GPCRs in different classes, the seven-TM helix motif is conserved throughout, and all GPCRs share a common topology. They can be grouped into three main classes: receptors related to rhodopsins (class A), secretin receptors (class B), and the metabotropic neurotransmitter receptors (class C). Of these, class A, the largest class, contains Ͼ1,200 distinct members and Ͼ7,000 putat...

IMPORTANCE Urinary tract infections are the most common infections in nursing home residents. However, most antibiotic use is for unlikely cystitis (ie, nonspecific symptoms and positive culture results secondary to asymptomatic bacteriuria or a urine sample improperly collected for culture) that is unnecessary and inappropriate. This antibiotic use is associated with an increased risk of antimicrobial resistance, adverse drug events, and Clostridioides difficile (formerly Clostridium difficile) infections.OBJECTIVE To determine the association of a multifaceted antimicrobial stewardship and quality improvement intervention with the reduction in unnecessary antimicrobial use for unlikely cystitis among noncatheterized nursing home residents. DESIGN, SETTING, AND PARTICIPANTSA quality improvement intervention evaluation was conducted to target antimicrobial use among residents with unlikely cystitis in 25 nursing homes across the United States. Baseline data were collected between

Background and aims The prevalence and significance of digestive manifestations in COVID-19 remain uncertain. We aimed to assess the prevalence, spectrum, severity, and significance of digestive manifestations in patients hospitalized with COVID-19. Methods Consecutive patients hospitalized with COVID-19 were identified across a geographically diverse alliance of medical centers in North America. Data pertaining to baseline characteristics, symptomatology, laboratory assessment, imaging, and endoscopic findings from the time of symptom onset until discharge or death were manually abstracted from electronic health records to characterize the prevalence, spectrum, and severity of digestive manifestations. Regression analyses were performed to evaluate the association between digestive manifestations and severe outcomes related to COVID-19. Findings A total of 1992 patients across 36 centers met eligibility criteria and were included. Overall, 53% of patients experienced at least one gastrointestinal symptom at any time during their illness, most commonly diarrhea (34%), nausea (27%), vomiting (16%), and abdominal pain (11%). In 74% of cases, gastrointestinal symptoms were judged to be mild. In total, 35% of patients developed an abnormal alanine aminotransferase or total bilirubin level; these were elevated to less than 5 times the upper limit of normal in 77% of cases. After adjusting for potential confounders, the presence of gastrointestinal symptoms at any time (odds ratio 0.93, 95% confidence interval 0.76-1.15) or liver test abnormalities on admission (odds ratio 1.31, 95% confidence interval 0.80-2.12) were not independently associated with mechanical ventilation or death. Conclusion Among patients hospitalized with COVID-19, gastrointestinal symptoms and liver test abnormalities were common but the majority were mild and their presence was not associated with a more severe clinical course.

The 2009 Family Smoking Prevention and Tobacco Control Act empowered the U.S. Food and Drug Administration to study "the impact of the use of menthol in cigarettes on the public health, including such use among children, African Americans, Hispanics and other racial and ethnic minorities," and develop recommendations. Current scientific evidence comparing human exposures between menthol and nonmenthol smokers shows mixed results. This is largely because of the many differences between commercial menthol and nonmenthol cigarettes other than their menthol content. We conducted an innovative study using two types of test cigarettes: a commercial nonmenthol brand that we mentholated at four different levels, and Camel Crush, a commercial cigarette containing a small capsule in the filter that releases menthol solution into the filter when crushed. Cigarettes were machine-smoked at each of the menthol levels investigated, and the total particulate matter (TPM) was collected on a quartz fiber filter pad and analyzed by gas chromatography/mass spectrometry for menthol, nicotine, tobacco-specific nitrosamines (TSNAs), polycyclic aromatic hydrocarbons (PAHs), cotinine, and quinoline. The mainstream smoke was also monitored continuously in real time on a puff-by-puff basis for seven gas-phase constituents (acetaldehyde, acetonitrile, acrylonitrile, benzene, 1,3-butadiene, isoprene, and 2,5-dimethylfuran), using a proton transfer reaction-mass spectrometer. Average yields (in micrograms/cigarette) for the analytes were determined. Menthol in the TPM samples increased linearly with applied menthol concentration, but the amounts of nicotine along with the target TSNAs, PAHs, cotinine, and quinoline in the cigarettes remained essentially unchanged. Similarly, yields of the targeted volatile organic compounds (VOCs) in whole smoke from the mentholated nonmenthol cigarettes that were measured in real-time were largely unaffected by their menthol levels. In the Camel Crush cigarettes, however, the VOC yields appeared to increase in the presence of menthol, especially in the gas phase. Although we succeeded in characterizing key mainstream smoke constituents in cigarettes that differ only in menthol content, further study is needed to definitively answer whether menthol affects exposure to selected cigarette constituents and thereby influences harm.

The panel identified 5 signs and symptoms likely indicative of uncomplicated cystitis in nursing home residents and developed a diagnostic algorithm that can be used to promote antibiotic stewardship in nursing homes. Given similarities in populations, the algorithm may also be applicable to the older adult and the broader post-acute/long-term care populations.