Reconstitution of the phosphodiesterase 6 maturation process important for photoreceptor cell function.

The sixth family phosphodiesterases (PDE6) are principal effector enzymes of the phototransduction cascade in rods and cones. Maturation of nascent PDE6 protein into a functional enzyme relies on a coordinated action of ubiquitous chaperone HSP90, its specialized cochaperone aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1), and the regulatory Pγ-subunit of PDE6. Deficits in PDE6 maturation and function underlie severe visual disorders and blindness. Here, to elucidate the roles of HSP90, AIPL1, and Pγ in the maturation process, we developed the heterologous expression system of human cone PDE6C in insect cells allowing characterization of the purified enzyme. We demonstrate that in the absence of Pγ, HSP90, and AIPL1 convert the inactive and aggregating PDE6C species into dimeric PDE6C that is predominantly misassembled. Nonetheless, a small fraction of PDE6C is properly assembled and fully functional. From the analysis of mutant mice that lack both rod Pγ and PDE6C, we conclude that, in contrast to the cone enzyme, no maturation of rod PDE6AB occurs in the absence of Pγ. Co-expression of PDE6C with AIPL1 and Pγ in insect cells leads to a fully mature enzyme that is equivalent to retinal PDE6. Lastly, using immature PDE6C and purified chaperone components, we reconstituted the process of the client maturation in vitro. Based on this analysis we propose a scheme for the PDE6 maturation process.

Ric-8A, a GEF, and a Chaperone for G Protein α-Subunits: Evidence for the Two-Faced Interface.

Resistance to inhibitors of cholinesterase 8A (Ric-8A) is a prominent non-receptor GEF and a chaperone of G protein α-subunits (Gα). Recent studies shed light on the structure of Ric-8A, providing insights into the mechanisms underlying its interaction with Gα. Ric-8A is composed of a core armadillo-like domain and a flexible C-terminal tail. Interaction of a conserved concave surface of its core domain with the Gα C-terminus appears to mediate formation of the initial Ric-8A/GαGDP intermediate, followed by the formation of a stable nucleotide-free complex. The latter event involves a large-scale dislocation of the Gα α5-helix that produces an extensive primary interface and disrupts the nucleotide-binding site of Gα. The distal portion of the C-terminal tail of Ric-8A forms a smaller secondary interface, which ostensibly binds the switch II region of Gα, facilitating binding of GTP. The two-site Gα interface of Ric-8A is distinct from that of GPCRs, and might have evolved to support the chaperone function of Ric-8A.

Structural basis for allosteric regulation of pyruvate kinase M2 by phosphorylation and acetylation.

Pyruvate kinase muscle isoform 2 (PKM2) is a key glycolytic enzyme and transcriptional coactivator and is critical for tumor metabolism. In cancer cells, native tetrameric PKM2 is phosphorylated or acetylated, which initiates a switch to a dimeric/monomeric form that translocates into the nucleus, causing oncogene transcription. However, it is not known how these post-translational modifications (PTMs) disrupt the oligomeric state of PKM2. We explored this question via crystallographic and biophysical analyses of PKM2 mutants containing residues that mimic phosphorylation and acetylation. We find that the PTMs elicit major structural reorganization of the fructose 1,6-bisphosphate (FBP), an allosteric activator, binding site, impacting the interaction with FBP and causing a disruption in oligomerization. To gain insight into how these modifications might cause unique outcomes in cancer cells, we examined the impact of increasing the intracellular pH (pHi) from ∼7.1 (in normal cells) to ∼7.5 (in cancer cells). Biochemical studies of WT PKM2 (wtPKM2) and the two mimetic variants demonstrated that the activity decreases as the pH is increased from 7.0 to 8.0, and wtPKM2 is optimally active and amenable to FBP-mediated allosteric regulation at pHi 7.5. However, the PTM mimetics exist as a mixture of tetramer and dimer, indicating that physiologically dimeric fraction is important and might be necessary for the modified PKM2 to translocate into the nucleus. Thus, our findings provide insight into how PTMs and pH regulate PKM2 and offer a broader understanding of its intricate allosteric regulation mechanism by phosphorylation or acetylation.

Large-scale conformational rearrangement of the α5-helix of Gα subunits in complex with the guanine nucleotide exchange factor Ric8A.

Resistance to inhibitors of cholinesterase 8A (Ric8A) protein is an important G protein-coupled receptor (GPCR)-independent regulator of G protein α-subunits (Gα), acting as a guanine nucleotide exchange factor (GEF) and a chaperone. Insights into the complex between Ric8A and Gα hold the key to understanding the mechanisms underlying noncanonical activation of G-protein signaling as well as the folding of nascent Gα proteins. Here, we examined the structure of the complex of Ric8A with minimized Gαi (miniGαi) in solution by small-angle X-ray scattering (SAXS) and exploited the scattering profile in modeling of the Ric8A/miniGαi complex by steered molecular dynamics (SMD) simulations. A small set of models of the complex featured minimal clash scores, excellent agreement with the experimental SAXS data, and a large-scale rearrangement of the signal-transducing α5-helix of Gα away from its ß-sheet core. The resulting interface involved the Gα α5-helix bound to the concave surface of Ric8A and the Gα ß-sheet that wraps around the C-terminal part of the Ric8A armadillo domain, leading to a severe disruption of the GDP-binding site. Further modeling of the flexible C-terminal tail of Ric8A indicated that it interacts with the effector surface of Gα. This smaller interface may enable the Ric8A-bound Gα to interact with GTP. The two-interface interaction with Gα described here distinguishes Ric8A from GPCRs and non-GPCR regulators of G-protein signaling.

Analysis of risk factors contributing to road traffic accidents in a tertiary care hospital. A hospital based cross-sectional study.

PURPOSE: Road traffic accidents (RTAs) are a public health issue and cost a lot to individuals, families, communities and nations. Trauma care systems in India are at a nascent stage of development. There is gross disparity between trauma services available in various parts of the country. Rural area in India has inefficient services for trauma care, due to the varied topography, financial constraints, and lack of appropriate health infrastructure. The present study is to study the trends of occurrence of RTA cases by month, week and time of accident occurrence as well as to research the types of vehicle involved in accidents and other various risk factors related to them. METHODS: During 1st January 2017 to 31st December 2017, a hospital-based and cross-sectional study of RTA victims was conducted. The patients were admitted in emergency department of Uttar Pradesh University of Medical Sciences, Saifai, Etawah, when stabilized, they were shifted to the orthopaedics and surgery ward. RESULTS: In the study, 654 road accident victims were included, of which the majority were males (77.5%) and the most of them belonged to rural (67%). RTA victims according to the month of occurrence majority were found in January (12.5%) and evening was time of a day with maximum accidents (32.1%). Mortality cases of RTA victims based on type of road user and it shows decreasing trend of mortality of motorcyclists (54.2%) followed by pedestrian (25.1%). CONCLUSION: There should be control over people driving vehicles under the influence of alcohol and drivers over-speeding and rash driving on urban roads as well as rural village roads.

Hyperbaric oxygen therapy as an adjuvant to standard therapy in the treatment of diabetic foot ulcers.

BACKGROUND AND AIMS: Chronic diabetic foot ulcers pose a major problem because of associated limb threatening complications. The aim of the present study was to evaluate the efficacy of hyperbaric oxygen therapy (HBOT) as an adjuvant to standard therapy for treatment of diabetic foot ulcers. MATERIAL AND METHODS: A total of 54 patients with diabetic foot ulcer of Wagner grade II-IV were recruited in this prospective, randomized, double blind study. Patients were randomized to receive HBOT along with standard therapy (group H; n = 28) or standard therapy alone (group S; n = 26). Patients were given 6 sessions per week for 6 weeks and followed up for 1 year. Outcomes were measured in terms of healing, and need for amputation, grafting or debridement. Parametric continuous variables were analyzed using Student unpaired t-test and categorical variables were analyzed using Chi square test. RESULTS: The diabetic ulcers in 78% patients in Group H completely healed without any surgical intervention while no patient in group S healed without surgical intervention (P = 0.001). 2 patients in group H required distal amputation while in Group S, three patients underwent proximal amputation. CONCLUSION: The present study shows that hyperbaric oxygen therapy is a useful adjuvant to standard therapy and is a better treatment modality if combined with standard treatment rather than standard treatment alone for management of diabetic foot ulcers.

Mechanistic and Structural Insights into Cysteine-Mediated Inhibition of Pyruvate Kinase Muscle Isoform 2.

Cancer cells regulate key enzymes in the glycolytic pathway to control the glycolytic flux, which is necessary for their growth and proliferation. One of the enzymes is pyruvate kinase muscle isoform 2 (PKM2), which is allosterically regulated by various small molecules. Using detailed biochemical and kinetic studies, we demonstrate that cysteine inhibits wild-type (wt) PKM2 by shifting from an active tetramer to a mixture of a tetramer and a less active dimer/monomer equilibrium and that the inhibition is dependent on cysteine concentration. The cysteine-mediated PKM2 inhibition is reversed by fructose 1,6-bisphosphate, an allosteric activator of PKM2. Furthermore, kinetic studies using two dimeric PKM2 variants, S437Y PKM2 and G415R PKM2, show that the reversal is caused by the tetramerization of wtPKM2. The crystal structure of the wtPKM2-Cys complex was determined at 2.25 Å, which showed that cysteine is held to the amino acid binding site via its main chain groups, similar to that observed for phenylalanine, alanine, serine, and tryptophan. Notably, ligand binding studies using fluorescence and isothermal titration calorimetry show that the presence of phosphoenolpyruvate alters the binding affinities of amino acids for wtPKM2 and vice versa, thereby unravelling the existence of a functionally bidirectional coupling between the amino acid binding site and the active site of wtPKM2.

Structural Investigation of a Dimeric Variant of Pyruvate Kinase Muscle Isoform 2.

Pyruvate kinase muscle isoform 2 (PKM2) catalyzes the terminal step in glycolysis, transferring a phosphoryl group from phosphoenolpyruvate to ADP, to produce pyruvate and ATP. PKM2 activity is allosterically regulated by fructose 1,6-bisphosphate (FBP), an upstream glycolytic intermediate. FBP stabilizes the tetrameric form of the enzyme. In its absence, the PKM2 tetramers dissociate, yielding a dimer-monomer mixture having lower enzymatic activity. The S437Y variant of PKM2 is incapable of binding FBP. Consistent with that defect, we find that S437Y exists in a monomer-dimer equilibrium in solution, with a Kd of ∼20 µM. Interestingly, however, the protein crystallizes as a tetramer, providing insight into the structural basis for impaired FBP binding of S437Y.

Structural studies of yeast Δ(1)-pyrroline-5-carboxylate dehydrogenase (ALDH4A1): active site flexibility and oligomeric state.

The proline catabolic enzyme Δ(1)-pyrroline-5-carboxylate dehydrogenase (ALDH4A1) catalyzes the NAD(+)-dependent oxidation of γ-glutamate semialdehyde to l-glutamate. In Saccharomyces cerevisiae, ALDH4A1 is encoded by the PUT2 gene and known as Put2p. Here we report the steady-state kinetic parameters of the purified recombinant enzyme, two crystal structures of Put2p, and the determination of the oligomeric state and quaternary structure from small-angle X-ray scattering and sedimentation velocity. Using Δ(1)-pyrroline-5-carboxylate as the substrate, catalytic parameters kcat and Km were determined to be 1.5 s(-1) and 104 µM, respectively, with a catalytic efficiency of 14000 M(-1) s(-1). Although Put2p exhibits the expected aldehyde dehydrogenase superfamily fold, a large portion of the active site is disordered in the crystal structure. Electron density for the 23-residue aldehyde substrate-binding loop is absent, implying substantial conformational flexibility in solution. We furthermore report a new crystal form of human ALDH4A1 (42% identical to Put2p) that also shows disorder in this loop. The crystal structures provide evidence of multiple active site conformations in the substrate-free form of the enzyme, which is consistent with a conformational selection mechanism of substrate binding. We also show that Put2p forms a trimer-of-dimers hexamer in solution. This result is unexpected because human ALDH4A1 is dimeric, whereas some bacterial ALDH4A1s are hexameric. Thus, global sequence identity and domain of life are poor predictors of the oligomeric states of ALDH4A1. Mutation of a single Trp residue that forms knob-in-hole interactions across the dimer-dimer interface abrogates hexamer formation, suggesting that this residue is the center of a protein-protein association hot spot.

Molecular basis of CRX/DNA recognition and stoichiometry at the Ret4 response element.

Two retinal transcription factors, cone-rod homeobox (CRX) and neural retina leucine zipper (NRL), cooperate functionally and physically to control photoreceptor development and homeostasis. Mutations in CRX and NRL cause severe retinal diseases. Despite the roles of NRL and CRX, insight into their functions at the molecular level is lacking. Here, we have solved the crystal structure of the CRX homeodomain in complex with its cognate response element (Ret4) from the rhodopsin proximal promoter region. The structure reveals an unexpected 2:1 stoichiometry of CRX/Ret4 and unique orientation of CRX molecules on DNA, and it explains the mechanisms of pathogenic mutations in CRX. Mutations R41Q and E42K disrupt the CRX protein-protein contacts based on the structure and reduce the CRX/Ret4 binding stoichiometry, suggesting a novel disease mechanism. Furthermore, we show that NRL alters the stoichiometry and increases affinity of CRX binding at the rhodopsin promoter, which may enhance transcription of rod-specific genes and suppress transcription of cone-specific genes.

Crystal structure of the bifunctional proline utilization A flavoenzyme from Bradyrhizobium japonicum.

The bifunctional proline catabolic flavoenzyme, proline utilization A (PutA), catalyzes the oxidation of proline to glutamate via the sequential activities of FAD-dependent proline dehydrogenase (PRODH) and NAD(+)-dependent Delta(1)-pyrroline-5-carboxylate dehydrogenase (P5CDH) domains. Although structures for some of the domains of PutA are known, a structure for the full-length protein has not previously been solved. Here we report the 2.1 A resolution crystal structure of PutA from Bradyrhizobium japonicum, along with data from small-angle x-ray scattering, analytical ultracentrifugation, and steady-state and rapid-reaction kinetics. PutA forms a ring-shaped tetramer in solution having a diameter of 150 A. Within each protomer, the PRODH and P5CDH active sites face each other at a distance of 41 A and are connected by a large, irregularly shaped cavity. Kinetics measurements show that glutamate production occurs without a lag phase, suggesting that the intermediate, Delta(1)-pyrroline-5-carboxylate, is preferably transferred to the P5CDH domain rather than released into the bulk medium. The structural and kinetic data imply that the cavity serves both as a microscopic vessel for the hydrolysis of Delta(1)-pyrroline-5-carboxylate to glutamate semialdehyde and a protected conduit for the transport of glutamate semialdehyde to the P5CDH active site.

Unique interface and dynamics of the complex of HSP90 with a specialized cochaperone AIPL1.

Photoreceptor phosphodiesterase PDE6 is central for visual signal transduction. Maturation of PDE6 depends on a specialized chaperone complex of HSP90 with aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1). Disruption of PDE6 maturation underlies a severe form of retina degeneration. Here, we report a 3.9 Å cryoelectron microscopy (cryo-EM) structure of the complex of HSP90 with AIPL1. This structure reveals a unique interaction of the FK506-binding protein (FKBP)-like domain of AIPL1 with HSP90 at its dimer interface. Unusually, the N terminus AIPL1 inserts into the HSP90 lumen in a manner that was observed previously for HSP90 clients. Deletion of the 7 N-terminal residues of AIPL1 decreased its ability to cochaperone PDE6. Multi-body refinement of the cryo-EM data indicated large swing-like movements of AIPL1-FKBP. Modeling the complex of HSP90 with AIPL1 using crosslinking constraints indicated proximity of the mobile tetratricopeptide repeat (TPR) domain with the C-terminal domain of HSP90. Our study establishes a framework for future structural studies of PDE6 maturation.

Estimation of Access to Safe Drinking Water to Households in Etawah District: A Cross-Sectional Study.

CONTEXT: Unsafe drinking water causes diarrheal disease and environmental enteropathy. The quality of water is determined by its physical, chemical, and biological characteristics. Water sources have a significant impact on household members' health, particularly children. To combat this, India is committed to providing household tap connections to ensure the delivery of safe drinking water with the "Jal Jeevan Mission." AIMS: This study aims to estimate the access to safe drinking water and the physical and chemical qualities of water (qualitatively) in the urban and rural areas of Etawah district, India. SETTINGS AND DESIGN: A cross-sectional study was conducted in Etawah district from January 2020 to December 2021. The study subjects were the eldest female of the family. A total of 312 females were included. The data collected were analyzed using IBM SPSS Statistics for Windows, version 25 (released 2017; IBM Corp., Armonk, New York, United States) for descriptive analysis. RESULTS: In the present study, 76.3% (238/312) of households in the urban and rural areas had access to safe drinking water (here, the meaning of the word "safe" is based on its operational definition). A total of 130 (83.3%) households in rural areas and only 21 (13.5%) in urban areas had private supply as the primary water source. The physical and chemical qualities of water were within the requirement (acceptable limit) and permissible limit in all the study areas, so the water is considered safe for drinking. CONCLUSIONS: This study reported that 76.3% (238) households had access to safe drinking water according to the operational definition. The major public source of drinking water was public-supplied tap water, and in private sources, submersible or boreholes were the most common.

Barriers of household toilet utilization among toilet owners in a rural area of Northern India: An analytical cross-sectional study.

Background: Open defecation continues to prevail among toilet owners despite effective implementation of the Swachh Bharat Mission (Gramin). We conducted this study to determine toilet utilization rates and learn about the barriers to toilet use in the rural areas. By understanding the barriers, physicians can provide targeted education and become better equipped to manage their patients' conditions and advocate for their demands. Materials and Methods: We conducted a cross-sectional study on the households of the rural field practice areas of the department in central Uttar Pradesh by the census method. House listing was procured from the departmental records. The questionnaire was directed at both the household level and individual level. Results: The proportion of households with access to a toilet was found to be 91.1% of which 504 households were included in the study. Among the toilet owners, 115 (22.8%) households were not using toilets exclusively by all the members. At the individual level, age groups (of 20-59 years, and ≥60 years) and female gender were found to be significantly associated with open defecation. At the household level, government assistance for toilet construction and livestock keeping was found to be associated with open defecation. Major barriers to toilet use were childhood habits, dearth of toilets in the farming grounds/workplace, women during menstruation and having a non-functional toilet. Conclusion: This study indicates that merely installing a household toilet does not ensure exclusive utilization of toilet and the practice of open defecation might continue to be prevalent if corrective measures are not undertaken.

Insulin sensitization by small molecules enhancing GLUT4 translocation.

Insulin resistance (IR) is the root cause of type II diabetes, yet no safe treatment is available to address it. Using a high throughput compatible assay that measures real-time translocation of the glucose transporter glucose transporter 4 (GLUT4), we identified small molecules that potentiate insulin action. In vivo, these insulin sensitizers improve insulin-stimulated GLUT4 translocation, glucose tolerance, and glucose uptake in a model of IR. Using proteomic and CRISPR-based approaches, we identified the targets of those compounds as Unc119 proteins and solved the structure of Unc119 bound to the insulin sensitizer. This study identifies compounds that have the potential to be developed into diabetes treatment and establishes Unc119 proteins as targets for improving insulin sensitivity.

Crystal structures and kinetics of monofunctional proline dehydrogenase provide insight into substrate recognition and conformational changes associated with flavin reduction and product release.

Proline dehydrogenase (PRODH) catalyzes the FAD-dependent oxidation of proline to Δ(1)-pyrroline-5-carboxylate, which is the first step of proline catabolism. Here, we report the structures of proline dehydrogenase from Deinococcus radiodurans in the oxidized state complexed with the proline analogue L-tetrahydrofuroic acid and in the reduced state with the proline site vacant. The analogue binds against the si face of the FAD isoalloxazine and is protected from bulk solvent by helix α8 and the ß1-α1 loop. The FAD ribityl chain adopts two conformations in the E-S complex, which is unprecedented for flavoenzymes. One of the conformations is novel for the PRODH superfamily and may contribute to the low substrate affinity of Deinococcus PRODH. Reduction of the crystalline enzyme-inhibitor complex causes profound structural changes, including 20° butterfly bending of the isoalloxazine, crankshaft rotation of the ribityl, shifting of α8 by 1.7 Å, reconfiguration of the ß1-α1 loop, and rupture of the Arg291-Glu64 ion pair. These changes dramatically open the active site to facilitate product release and allow electron acceptors access to the reduced flavin. The structures suggest that the ion pair, which is conserved in the PRODH superfamily, functions as the active site gate. Mutagenesis of Glu64 to Ala decreases the catalytic efficiency 27-fold, which demonstrates the importance of the gate. Mutation of Gly63 decreases the efficiency 140-fold, which suggests that flexibility of the ß1-α1 loop is essential for optimal catalysis. The large conformational changes that are required to form the E-S complex suggest that conformational selection plays a role in substrate recognition.

Proline: Mother Nature's cryoprotectant applied to protein crystallography.

L-Proline is one of Mother Nature's cryoprotectants. Plants and yeast accumulate proline under freeze-induced stress and the use of proline in the cryopreservation of biological samples is well established. Here, it is shown that L-proline is also a useful cryoprotectant for protein crystallography. Proline was used to prepare crystals of lysozyme, xylose isomerase, histidine acid phosphatase and 1-pyrroline-5-carboxylate dehydrogenase for low-temperature data collection. The crystallization solutions in these test cases included the commonly used precipitants ammonium sulfate, sodium chloride and polyethylene glycol and spanned the pH range 4.6-8.5. Thus, proline is compatible with typical protein-crystallization formulations. The proline concentration needed for cryoprotection of these crystals is in the range 2.0-3.0 M. Complete data sets were collected from the proline-protected crystals. Proline performed as well as traditional cryoprotectants based on the diffraction resolution and data-quality statistics. The structures were refined to assess the binding of proline to these proteins. As observed with traditional cryoprotectants such as glycerol and ethylene glycol, the electron-density maps clearly showed the presence of proline molecules bound to the protein. In two cases, histidine acid phosphatase and 1-pyrroline-5-carboxylate dehydrogenase, proline binds in the active site. It is concluded that L-proline is an effective cryoprotectant for protein crystallography.

Assessment of knowledge and their practices regarding malaria among members of Village Health Sanitation Committee in rural Uttar Pradesh: A cross-sectional study.

Background: In 2019, the global number of malaria cases was estimated at 229 million. An estimated 409,000 deaths were attributed to malaria in 2019. Under-five children are the most susceptible to malaria, accounting for 67% (274,000) of all malaria deaths worldwide in 2019. This study aimed to assess knowledge and practices regarding malaria among Village Health Sanitation Committee (VHSC) members in rural Uttar Pradesh. Methodology: This cross-sectional study was conducted in the villages of four districts of Uttar Pradesh with high malaria burden. In the present study, 484 participants were interviewed from four districts of Uttar Pradesh. Results: Nearly all the participants (97.1%) have heard about malaria. Majority of the participants (97.1) were aware that mosquito bites spread malaria. However, many participants were also having a false awareness that malaria is spread by other modes like drinking contaminated water, touching each other, eating contaminated food, and so on. More than half of the participants told that mosquitoes are responsible for malaria breeds in stagnant clean water (25.6%) and stagnant dirty water (28.5%). Nearly half of them were aware that mosquitoes' biting time was sunset (42.1%) and sunrise (7.8%). Conclusion: In the present study, many participants were having a false awareness that malaria is spread by other modes like drinking contaminated water, touching each other, eating contaminated food, and so on. Even the knowledge regarding any government program for the prevention and control of malaria of the mosquitoes was very weak. There is an urgent requirement of increasing knowledge among the VHSC members to reduce the malaria burden in the country.

Modified Bain's Circuit as an Alternate to Non-invasive Ventilation in COVID 19.

Introduction COVID-19 is a pandemic that severely affects the lungs. Symptomatically affected individuals often become severely hypoxic, requiring non-invasive ventilation. The scarcity of resources in resource-compromised countries like India led to the adoption of novel strategies like using Bain's circuit for assisting spontaneous ventilation. This study compares the outcome when a standard circuit is replaced with a shortened Bain's circuit. Aims and objectives To compare shortened Bain's circuit and bilevel positive airway pressure (BiPAP) in spontaneously ventilated COVID 19 patients with regards to effects on hemodynamic stability and efficacy of ventilation using blood gas analysis. Methodology Twenty-four COVID patients aged between 35-70 years, requiring non-invasive ventilation but not tolerating BiPAP or not improving on BiPAP were enrolled in the study. Baseline heart rate and arterial blood gases (ABG) were recorded. Patients were then ventilated using shortened Bain's circuit. Heart rate and ABG were then recorded two hours after ventilation. Results Hemodynamic and blood gas parameters were comparable between the two groups at baseline and on BiPAP. Group A showed better hemodynamic and blood gas profiles compared to group B, but the difference was not statistically significant because of small sample size. Conclusion Shortened Bain's circuit may be a viable alternative to non-invasive ventilation in spontaneously breathing hypoxic patients with efficacy comparable to a standard Bain's circuit and reduced chances of carbon dioxide retention. Studies with a larger sample size are needed to further validate the conclusion.

Frmpd1 Facilitates Trafficking of G-Protein Transducin and Modulates Synaptic Function in Rod Photoreceptors of Mammalian Retina.

Trafficking of transducin (Gαt) in rod photoreceptors is critical for adaptive and modulatory responses of the retina to varying light intensities. In addition to fine-tuning phototransduction gain in rod outer segments (OSs), light-induced translocation of Gαt to the rod synapse enhances rod to rod bipolar synaptic transmission. Here, we show that the rod-specific loss of Frmpd1 (FERM and PDZ domain containing 1), in the retina of both female and male mice, results in delayed return of Gαt from the synapse back to outer segments in the dark, compromising the capacity of rods to recover from light adaptation. Frmpd1 directly interacts with Gpsm2 (G-protein signaling modulator 2), and the two proteins are required for appropriate sensitization of rod-rod bipolar signaling under saturating light conditions. These studies provide insight into how the trafficking and function of Gαt is modulated to optimize the photoresponse and synaptic transmission of rod photoreceptors in a light-dependent manner.