Ligand-induced transmembrane conformational coupling in monomeric EGFR

Single pass cell surface receptors regulate cellular processes by transmitting ligand-encoded signals across the plasma membrane via changes to their extracellular and intracellular conformations. This transmembrane signaling is generally initiated by ligand binding to the receptors in their monomeric form. While subsequent receptor-receptor interactions are established as key aspects of transmembrane signaling, the contribution of monomeric receptors has been challenging to isolate due to the complexity and ligand-dependence of these interactions. By combining membrane nanodiscs produced with cell-free expression, single-molecule Förster Resonance Energy Transfer measurements, and molecular dynamics simulations, we report that ligand binding induces intracellular conformational changes within monomeric, full-length epidermal growth factor receptor (EGFR). Our observations establish the existence of extracellular/intracellular conformational coupling within a single receptor molecule. We implicate a series of electrostatic interactions in the conformational coupling and find the coupling is inhibited by targeted therapeutics and mutations that also inhibit phosphorylation in cells. Collectively, these results introduce a facile mechanism to link the extracellular and intracellular regions through the single transmembrane helix of monomeric EGFR, and raise the possibility that intramolecular transmembrane conformational changes upon ligand binding are common to single-pass membrane proteins.

Osteosynthesis of Neck of Femur Fracture below 65 years of Age: does timing of surgery influence osteonecrosis, nonunion and functional outcome?

Background Influence of timing of injury surgery interval in outcome of osteosynthesis of neck of femur has always been a matter of debate. Patients in our set up have been surgically treated for neck of femur fracture with wide range of injury surgery interval which could have resulted in varied functional outcome and radiological outcome. Objective To evaluate the difference in functional outcome, femoral head osteonecrosis and non-union in fracture neck of femur fixed within and after twenty-four hours. Method All patients, who had undergone osteosynthesis for the neck of femur fractures via open or closed technique from 2010 to 2018 were analyzed retrospectively. The cases were examined and evaluated in terms of injury surgery interval, fracture union, functional status using Modified Harris Hip Score, complications like femoral head osteonecrosis and non-union. Result Fifty patients with an average injury surgery interval of 34±28 hours were evaluated. Twenty three (46%) cases were included in early surgery group (< 24 hours) and 27 (54%) patients were included in delayed (> 24 hours) surgery group. Incidence of femoral head osteonecrosis was reported in two (4%) cases, both being in delayed fixation group (p=0.49). Non-union was reported in four (8%) patients, one in early fixation group and three in delayed fixation group (p=0.61). The average Modified Harris Hip Score in early fixation group was 87 and in delayed fixation group was 84 (p=0.1). Forty two (84%) cases had a good quality of reduction and eight (16%) had a poor reduction. Non-union and functional outcome significantly differed between the good and poor reduction group (p=0.001 and 0.004 respectively). Conclusion There is no significant difference in the functional and radiological outcome of cases operated before and after 24 hours for osteosynthesis of neck of femur fractures in patients 16 to 65 years age group. However, poor reduction is significantly associated with the increased rate of non-union and poor functional outcome.

Phosphorylation-Dependent Conformations of the Disordered Carboxyl-Terminus Domain in the Epidermal Growth Factor Receptor

The epidermal growth factor receptor (EGFR), a receptor tyrosine kinase, regulates basic cellular functions and is a major target for anticancer therapeutics. The carboxyl-terminus domain is a disordered region of EGFR that contains the tyrosine residues, which undergo autophosphorylation followed by docking of signaling proteins. Local phosphorylation-dependent secondary structure has been identified and is thought to be associated with the signaling cascade. Deciphering and distinguishing the overall conformations, however, have been challenging because of the disordered nature of the carboxyl-terminus domain and resultant lack of well-defined three-dimensional structure for most of the domain. We investigated the overall conformational states of the isolated EGFR carboxyl-terminus domain using single-molecule Förster resonance energy transfer and coarse-grained simulations. Our results suggest that electrostatic interactions between charged residues emerge within the disordered domain upon phosphorylation, producing a looplike conformation. This conformation may enable binding of downstream signaling proteins and potentially reflect a general mechanism in which electrostatics transiently generate functional architectures in disordered regions of a well-folded protein.

Optical Antenna-Based Fluorescence Correlation Spectroscopy to Probe the Nanoscale Dynamics of Biological Membranes

The plasma membrane of living cells is compartmentalized at multiple spatial scales ranging from the nano- to the mesoscale. This nonrandom organization is crucial for a large number of cellular functions. At the nanoscale, cell membranes organize into dynamic nanoassemblies enriched by cholesterol, sphingolipids, and certain types of proteins. Investigating these nanoassemblies known as lipid rafts is of paramount interest in fundamental cell biology. However, this goal requires simultaneous nanometer spatial precision and microsecond temporal resolution, which is beyond the reach of common microscopes. Optical antennas based on metallic nanostructures efficiently enhance and confine light into nanometer dimensions, breaching the diffraction limit of light. In this Perspective, we discuss recent progress combining optical antennas with fluorescence correlation spectroscopy (FCS) to monitor microsecond dynamics at nanoscale spatial dimensions. These new developments offer numerous opportunities to investigate lipid and protein dynamics in both mimetic and native biological membranes.

Planar Optical Nanoantennas Resolve Cholesterol-Dependent Nanoscale Heterogeneities in the Plasma Membrane of Living Cells

Optical nanoantennas can efficiently confine light into nanoscopic hotspots, enabling single-molecule detection sensitivity at biological relevant conditions. This innovative approach to breach the diffraction limit offers a versatile platform to investigate the dynamics of individual biomolecules in living cell membranes and their partitioning into cholesterol-dependent lipid nanodomains. Here, we present optical nanoantenna arrays with accessible surface hotspots to study the characteristic diffusion dynamics of phosphoethanolamine (PE) and sphingomyelin (SM) in the plasma membrane of living cells at the nanoscale. Fluorescence burst analysis and fluorescence correlation spectroscopy performed on nanoantennas of different gap sizes show that, unlike PE, SM is transiently trapped in cholesterol-enriched nanodomains of 10 nm diameter with short characteristic times around 100 μs. The removal of cholesterol led to the free diffusion of SM, consistent with the dispersion of nanodomains. Our results are consistent with the existence of highly transient and fluctuating nanoscale assemblies enriched by cholesterol and sphingolipids in living cell membranes, also known as lipid rafts. Quantitative data on sphingolipids partitioning into lipid rafts is crucial to understand the spatiotemporal heterogeneous organization of transient molecular complexes on the membrane of living cells at the nanoscale. The proposed technique is fully biocompatible and thus provides various opportunities for biophysics and live cell research to reveal details that remain hidden in confocal diffraction-limited measurements.

Transient Nanoscopic Phase Separation in Biological Lipid Membranes Resolved by Planar Plasmonic Antennas

Nanoscale membrane assemblies of sphingolipids, cholesterol, and certain proteins, also known as lipid rafts, play a crucial role in facilitating a broad range of important cell functions. Whereas on living cell membranes lipid rafts have been postulated to have nanoscopic dimensions and to be highly transient, the existence of a similar type of dynamic nanodomains in multicomponent lipid bilayers has been questioned. Here, we perform fluorescence correlation spectroscopy on planar plasmonic antenna arrays with different nanogap sizes to assess the dynamic nanoscale organization of mimetic biological membranes. Our approach takes advantage of the highly enhanced and confined excitation light provided by the nanoantennas together with their outstanding planarity to investigate membrane regions as small as 10 nm in size with microsecond time resolution. Our diffusion data are consistent with the coexistence of transient nanoscopic domains in both the liquid-ordered and the liquid-disordered microscopic phases of multicomponent lipid bilayers. These nanodomains have characteristic residence times between 30 and 150 μs and sizes around 10 nm, as inferred from the diffusion data. Thus, although microscale phase separation occurs on mimetic membranes, nanoscopic domains also coexist, suggesting that these transient assemblies might be similar to those occurring in living cells, which in the absence of raft-stabilizing proteins are poised to be short-lived. Importantly, our work underscores the high potential of photonic nanoantennas to interrogate the nanoscale heterogeneity of native biological membranes with ultrahigh spatiotemporal resolution.

In-Plane Plasmonic Antenna Arrays with Surface Nanogaps for Giant Fluorescence Enhancement

Optical nanoantennas have a great potential for enhancing light-matter interactions at the nanometer scale, yet fabrication accuracy and lack of scalability currently limit ultimate antenna performance and applications. In most designs, the region of maximum field localization and enhancement (i.e., hotspot) is not readily accessible to the sample because it is buried into the nanostructure. Moreover, current large-scale fabrication techniques lack reproducible geometrical control below 20 nm. Here, we describe a new nanofabrication technique that applies planarization, etch back, and template stripping to expose the excitation hotspot at the surface, providing a major improvement over conventional electron beam lithography methods. We present large flat surface arrays of in-plane nanoantennas, featuring gaps as small as 10 nm with sharp edges, excellent reproducibility and full surface accessibility of the hotspot confined region. The novel fabrication approach drastically improves the optical performance of plasmonic nanoantennas to yield giant fluorescence enhancement factors up to 10⁴-10⁵ times, together with nanoscale detection volumes in the 20 zL range. The method is fully scalable and adaptable to a wide range of antenna designs. We foresee broad applications by the use of these in-plane antenna geometries ranging from large-scale ultrasensitive sensor chips to microfluidics and live cell membrane investigations.

All-Dielectric Silicon Nanogap Antennas To Enhance the Fluorescence of Single Molecules

Plasmonic antennas have a profound impact on nanophotonics as they provide efficient means to manipulate light and enhance light-matter interactions at the nanoscale. However, the large absorption losses found in metals can severely limit the plasmonic applications in the visible spectral range. Here, we demonstrate the effectiveness of an alternative approach using all-dielectric nanoantennas based on silicon dimers to enhance the fluorescence detection of single molecules. The silicon antenna design is optimized to confine the near-field intensity in the 20 nm nanogap and reach a 270-fold fluorescence enhancement in a nanoscale volume of λ(3)/1800 with dielectric materials only. Our conclusions are assessed by combining polarization resolved optical spectroscopy of individual antennas, scanning electron microscopy, numerical simulations, fluorescence lifetime measurements, fluorescence burst analysis, and fluorescence correlation spectroscopy. This work demonstrates that all-silicon nanoantennas are a valid alternative to plasmonic devices for enhanced single molecule fluorescence sensing, with the additional key advantages of reduced nonradiative quenching, negligible heat generation, cost-efficiency, and complementary metal-oxide-semiconductor (CMOS) compatibility.

Nanoscale volume confinement and fluorescence enhancement with double nanohole aperture

Diffraction ultimately limits the fluorescence collected from a single molecule, and sets an upper limit to the maximum concentration to isolate a single molecule in the detection volume. To overcome these limitations, we introduce here the use of a double nanohole structure with 25 nm gap, and report enhanced detection of single fluorescent molecules in concentrated solutions exceeding 20 micromolar. The nanometer gap concentrates the light into an apex volume down to 70 zeptoliter (10(-21) L), 7000-fold below the diffraction-limited confocal volume. Using fluorescence correlation spectroscopy and time-correlated photon counting, we measure fluorescence enhancement up to 100-fold, together with local density of optical states (LDOS) enhancement of 30-fold. The distinctive features of double nanoholes combining high local field enhancement, efficient background screening and relative nanofabrication simplicity offer new strategies for real time investigation of biochemical events with single molecule resolution at high concentrations.

The Ponseti method in the treatment of children with idiopathic clubfoot presenting between five and ten years of age

Our goal was to evaluate the use of Ponseti's method, with minor adaptations, in the treatment of idiopathic clubfeet presenting in children between five and ten years of age. A retrospective review was performed in 36 children (55 feet) with a mean age of 7.4 years (5 to 10), supplemented by digital images and video recordings of gait. There were 19 males and 17 females. The mean follow-up was 31.5 months (24 to 40). The mean number of casts was 9.5 (6 to 11), and all children required surgery, including a percutaneous tenotomy or open tendo Achillis lengthening (49%), posterior release (34.5%), posterior medial soft-tissue release (14.5%), or soft-tissue release combined with an osteotomy (2%). The mean dorsiflexion of the ankle was 9° (0° to 15°). Forefoot alignment was neutral in 28 feet (51%) or adducted (< 10°) in 20 feet (36%), > 10° in seven feet (13%). Hindfoot alignment was neutral or mild valgus in 26 feet (47%), mild varus (< 10°) in 19 feet (35%), and varus (> 10°) in ten feet (18%). Heel-toe gait was present in 38 feet (86%), and 12 (28%) exhibited weight-bearing on the lateral border (out of a total of 44 feet with gait videos available for analysis). Overt relapse was identified in nine feet (16%, six children). The parents of 27 children (75%) were completely satisfied. A plantigrade foot was achieved in 46 feet (84%) without an extensive soft-tissue release or bony procedure, although under-correction was common, and longer-term follow-up will be required to assess the outcome.

Spatial filtering nearly eliminates the side-lobes in single- and multi-photon 4pi-type-C super-resolution fluorescence microscopy

Super-resolution microscopy has tremendously progressed our understanding of cellular biophysics and biochemistry. Specifically, 4pi fluorescence microscopy technique stands out because of its axial super-resolution capability. All types of 4pi-microscopy techniques work well in conjugation with deconvolution techniques to get rid of artifacts due to side-lobes. In this regard, we propose a technique based on spatial filter in a 4pi-type-C confocal setup to get rid of these artifacts. Using a special spatial filter, we have reduced the depth-of-focus. Interference of two similar depth-of-focus beams in a 4π geometry result in substantial reduction of side-lobes. Studies show a reduction of side-lobes by 46% and 76% for single and two photon variant compared to 4pi - type - C confocal system. This is incredible considering the resolving capability of the existing 4pi - type - C confocal microscopy. Moreover, the main lobe is found to be 150 nm for the proposed spatial filtering technique as compared to 690 nm of the state-of-art confocal system. Reconstruction of experimentally obtained 2PE - 4pi data of green fluorescent protein (GFP)-tagged mitocondrial network shows near elimination of artifacts arising out of side-lobes. Proposed technique may find interesting application in fluorescence microscopy, nano-lithography, and cell biology.

Transthoracic echocardiography may be useful for preoperative cardiac evaluation of gynaecological patients undergoing routine surgery

Echocardiography has been an integral noninvasive tool for [preoperative] cardiac evaluation that provides with echocardiographic details which may also be useful to perioperative clinicians to tailor their anesthetic deliberation while dealing with preoperative patients. The objective of this study is preoperative evaluation of routine gynecological patients echocardiographically after being referred from respective internists or anesthesiologists. This was a prospective, nonrandomized study of elective 68 cases who underwent echocardiographic evaluation preoperatively from 15th July 2009 to 14th July 2012. The mean age of the patients was 52.1 +/- 10.3 years with the age range of 30-79 years. Valvular heart disease was the most common echocardiographic finding (129.4%) followed by left ventricular diastolic dysfunction, LVDD (48.5%) and left ventricular hypertrophy (22.1%). Systolic dysfunction was detected in 2.9% of patients and pulmonary arterial hypertension in 2.9% patients. Amongst patients referred after preoperative anaesthetic evaluation, patients had different cardiac lesions echocardiographically. Preoperative echocardiographic evaluation may provide important cardiac informations and values which might be employed by perioperative physicians to tailor their treatment.

SU-D-BRA-03: Simultaneous MV-KV Imaging for Intra-Fractional Motion Management during Volume Modulated Arc Therapy (VMAT) Delivery on the Varian TrueBeam

PURPOSE

To evaluate a MV-kV intra-fractional imaging technique for use during volume modulated arc therapy (VMAT) with the Varian TrueBeam.

METHODS

MV-kV image pairs were acquired intra-fractionally during VMAT delivery. kV images (11 fps) were acquired throughout delivery using a standard pre-programmed imaging template. MV images (9.5 fps) were acquired simultaneously by deploying the EPID and passively collecting the resulting images using Varian proprietary software, iTools Capture. Localization accuracy was evaluated by imaging a Rando phantom implanted with 3 fiducials while moving the couch according to XML- programmed trajectories simulating typical prostate and respiratory motion. VMAT delivery was done using a single 360 degree arc in TrueBeam Developer mode. The effect on accuracy of total MU and gantry speed was studied. To improve image quality, MV frame averaging was performed and the MV and kV images were then registered to their corresponding DRRs using in-house registration software. From these 2D registrations, the 3D position at each MV-kV acquisition point was determined.

RESULTS

Between 130 and 390 MV-kV pairs were acquired for each delivery. The mean difference between planned couch and measured fiducial 3D positions with prostate motion was less than 0.03 cm in each direction (SD 0.03 cm). Neither gantry speed nor MU significantly impacted accuracy. for respiratory motion, the mean difference between planned and measured position was less than 0.04 cm. Standard deviation averaged 0.06 cm but increased to 0.12 cm with large instantaneous motion and less MV dose per frame. MV frame averaging and inaccuracies in MV image gantry angle determination also affected accuracy, particularly with significant motion.

CONCLUSIONS

With high quality MV imaging, MV-kV localization techniques can be highly accurate, even in the presence of significant motion. As clinical MV-kV methods become available, such techniques can provide an efficient and accurate method for monitoring intra-fractional motion. This work was partially supported through a research agreement with Varian Medical Systems, Palo Alto, CA.

Conservative treatment in acute appendicitis

INTRODUCTION: Acute appendicitis is one of the commonest surgical problems and appendectomy is one of the most commonly done operations in the emergency world wide. Though there have been occasional reports with conservative treatment in acute appendicitis, it is not being practiced as a routine. METHODS: All patients between ten to sixty years of age admitted at BPKIHS with the diagnosis of acute appendicitis over a period of one year were enrolled in the study. After taking informed consent the patients were managed conservatively. Those who did not respond to antibiotics within 24 hours were operated. Total hospital stay and complications were recorded and they were followed up at first week, sixth week and sixth month. The success rate, conversion rate, recurrence rate and morbidity and mortality pattern were assessed as the final outcome of conservative treatment of acute appendicitis. RESULTS: A total of 96 patients (48 males and 48 females) underwent conservative treatment. The conservative treatment was successful in 79 (82.3%) cases and failed in 11 (11.4%) cases, which included: conversion to appendectomy during conservative treatment period 4 (4.2%) cases, recurrence 7 (7.3%) cases. There was no mortality in this study. CONCLUSION: Acute appendicitis can be treated successfully with conservative (antibiotics) treatment with a short hospital stay. Though there is a risk of recurrence in some cases, all the complications after appendectomy can be eliminated with the conservative treatment.Keywords: acute appendicitis, appendicular lump, conservative management

Perioperative intravenous lidocaine infusion on postoperative pain relief in patients undergoing upper abdominal surgery

Due to unpleasant nature and physiological consequences of postoperative pain, search of safe and effective modalities for its management has remained a subject of interest to clinical researchers. Analgesic action of lidocaine infusion in patients with chronic neuropathic pain is well known but its place in relieving postoperative pain is yet to be established. The study aimed to assess the effectiveness of perioperative intravenous lidocaine infusion on postoperative pain intensity and analgesic requirement. Sixty patients undergoing major upper abdominal surgery were recruited in this randomized double blinded study. Thirty patients received lidocaine 2.0% (intravenous bolus 1.5 mg/kg followed by an infusion of 1.5 mg/kg/h), and 30 patients received normal saline according to randomization. The infusion started 30 min before skin incision and stopped 1 h after the end of surgery. Postoperative pain intensity and analgesic (diclofenac) requirement were assessed at the interval 15 minutes for 1 hour then 4 hourly up to 24 hours. The pain intensity at rest and movement as well as the total postoperative analgesic (diclofenac) requirement were significantly lower (142.50 +/- 37.80 mg vs.185.00 +/- 41.31 mg, P<0.001) in lidocaine group. The extubation time was significantly longer in lidocaine group (14.43 +/- 3.50 minutes vs. 6.73 +/- 1.76 minutes, P<0.001). The time for the first dose of analgesic requirement was longer in lidocaine group (60.97 +/- 18.05 minutes vs.15.73 +/- 7.46 minutes, P<0.001). It can be concluded that perioperative infusion of low dose of lidocaine decreases the intensity of postoperative pain, reduces the postoperative analgesic consumption, without causing significant adverse effects in patients undergoing upper abdominal surgery.

Conservative treatment in acute appendicitis

INTRODUCTION

Acute appendicitis is one of the commonest surgical problems and appendectomy is one of the most commonly done operations in the emergency world wide. Though there have been occasional reports with conservative treatment in acute appendicitis, it is not being practiced as a routine.

METHODS

All patients between ten to sixty years of age admitted at BPKIHS with the diagnosis of acute appendicitis over a period of one year were enrolled in the study. After taking informed consent the patients were managed conservatively. Those who did not respond to antibiotics within 24 hours were operated. Total hospital stay and complications were recorded and they were followed up at first week, sixth week and sixth month. The success rate, conversion rate, recurrence rate and morbidity and mortality pattern were assessed as the final outcome of conservative treatment of acute appendicitis.

RESULTS

A total of 96 patients (48 males and 48 females) underwent conservative treatment. The conservative treatment was successful in 79 (82.3%) cases and failed in 11 (11.4%) cases, which included: conversion to appendectomy during conservative treatment period 4 (4.2%) cases, recurrence 7 (7.3%) cases. There was no mortality in this study.

CONCLUSION

Acute appendicitis can be treated successfully with conservative (antibiotics) treatment with a short hospital stay. Though there is a risk of recurrence in some cases, all the complications after appendectomy can be eliminated with the conservative treatment.

Pediatric femoral hernia

Pediatric femoral hernias account for less than 1% of all groin hernias. Pediatric femoral hernias are rather uncommon more so in males, often overlooked, misdiagnosed and treated as inguinal hernia. Femoral hernia masquerading as inguinal hernia in a seven year old male is reported along with review of relevant literature.

Pediatric Femoral Hernia

Pediatric femoral hernias account for less than 1% of all groin hernias. Pediatric femoral hernias arerather uncommon more so in males, often overlooked, misdiagnosed and treated as inguinal hernia.Femoral hernia masquerading as inguinal hernia in a seven year old male is reported along withreview of relevant literature.Key Words: children, femoral, hernia, misdiagnosed

Iliopsoas abscess: analysis and perspectives from an endemic region of Eastern Nepal

OBJECTIVE

To evaluate the clinical profile and outcome in patients with iliopsoas abscess.

METHODS

A descriptive study was carried out in B.P. Koirala Institute of Health Science, Dharan, Nepal from February 2005 to March 2006. The medical records of all thirty six patients admitted in surgery ward with diagnosis of iliopsoas abscess during the study period were analyzed.

RESULTS

Thirty six patients were included the study. There were 22 (61.1%) males and 14 (38.9%) females with a mean age of 24.33 +/-19.19 years. Demographic distribution of the patients revealed the highest number 13 (36.1%) from Sunsari district, eastern part of the country. Right sided unilateral involvement was the most common presentation and only 2 cases had bilateral involvement. In none of our patients the dorsolumbar spine radiograph revealed any involvement of the bone. The most common complaints were pain in lower abdomen and lump in iliac fossa with flexion deformity at hip joint. All the patients underwent open surgical drainage and their outcomes were analyzed in term of cure, morbidity and mortality. Staphylococcus aureus was the most common organism 24 (61.5%) isolated. Twenty two (91.66%) of Staphylococcus aureus samples were sensitive to ciprofloxacin. There was one mortality in the group who died of septicaemia secondary to necrotizing fascitis. Six patients had wound infection, which were cured by regular dressing.

CONCLUSION

On the basis of our experience and review of available relevant literature, we can conclude that a high index of suspicion and awareness of the varying clinical picture are required to diagnose this condition properly. Ultrasonography should still be the preferred imaging modality as it is cheap, safe, cost effective and readily available. Ciprofloxacin should be used as a first line drug. Image guided aspiration may be practical in selected cases having little pus and traditional open drainage should be considered without hesitation.

Splenic epidermoid cyst

Splenic epidermoid cyst is a rare cystic disease affecting the spleen. We report a young male who presented with a painless abdominal lump. Ultrasonography and CT scan of abdomen showed a huge cystic lesion of obscure origin. At laparotomy a huge cyst was found to be arising from the superior pole of the spleen, and its removal necessitated splenectomy. Histopathological findings were consistent with splenic epidermoid cyst. The aetiopathology and different treatment modalities of splenic cysts are discussed.