Anti-Brownian traps confine single particles in free solution by closed-loop feedback forces that directly counteract Brownian motion. Extended-duration measurements on trapped objects allow detailed ...characterization of photophysical and transport properties as well as observation of infrequent or rare dynamics. However, this approach has been generally limited to particles that can be tracked by fluorescence emission. Here we present the Interferometric Scattering Anti-Brownian ELectrokinetic (ISABEL) trap, which uses interferometric scattering rather than fluorescence to monitor particle position. By decoupling the ability to track (and therefore trap) a particle from collection of its spectroscopic data, the ISABEL trap enables confinement and extended study of single particles that do not fluoresce, only weakly fluoresce, or exhibit intermittent fluorescence or photobleaching. This new technique significantly expands the range of nanoscale objects that may be investigated at the single-particle level in free solution.
Carboxysomes are self-assembled bacterial microcompartments that facilitate carbon assimilation by colocalizing the enzymes of CO2 fixation within a protein shell. These microcompartments can be ...highly heterogeneous in their composition and filling, so measuring the mass and loading of an individual carboxysome would allow for better characterization of its assembly and function. To enable detailed and extended characterizations of single nanoparticles in solution, we recently demonstrated an improved interferometric scattering anti-Brownian electrokinetic (ISABEL) trap, which tracks the position of a single nanoparticle via its scattering of a near-infrared beam and applies feedback to counteract its Brownian motion. Importantly, the scattering signal can be related to the mass of nanoscale proteinaceous objects, whose refractive indices are well-characterized. We calibrate single-particle scattering cross-section measurements in the ISABEL trap and determine individual carboxysome masses in the 50–400 MDa range by analyzing their scattering cross sections with a core–shell model. We further investigate carboxysome loading by combining mass measurements with simultaneous fluorescence reporting from labeled internal components. This method may be extended to other biological objects, such as viruses or extracellular vesicles, and can be combined with orthogonal fluorescence reporters to achieve precise physical and chemical characterization of individual nanoscale biological objects.
Diffusion of biological nanoparticles in solution impedes our ability to continuously monitor individual particles and measure their physical and chemical properties. To overcome this, we previously ...developed the interferometric scattering anti-Brownian electrokinetic (ISABEL) trap, which uses scattering to localize a particle and applies electrokinetic forces that counteract Brownian motion, thus enabling extended observation. Here we present an improved ISABEL trap that incorporates a near-infrared scatter illumination beam and rapidly interleaves 405 and 488 nm fluorescence excitation reporter beams. With the ISABEL trap, we monitored the internal redox environment of individual carboxysomes labeled with the ratiometric redox reporter roGFP2. Carboxysomes widely vary in scattering contrast (reporting on size) and redox-dependent ratiometric fluorescence. Furthermore, we used redox sensing to explore the chemical kinetics within intact carboxysomes, where bulk measurements may contain unwanted contributions from aggregates or interfering fluorescent proteins. Overall, we demonstrate the ISABEL trap’s ability to sensitively monitor nanoscale biological objects, enabling new experiments on these systems.
Automobile exhaust derived air pollutants have become a major health hazard. Coupled with the inhalation of fuel vapour, as occurs in petrol station workers, this may lead to significant impairment ...of lung function. Spirometric lung functions were studied in 58 petrol station workers to examine this possibility. The forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), forced expiratory flow 25%-75% (FEF25-75) and peak expiratory flow (PEF) were recorded and analysed separately for smokers and non-smokers. The workers were divided into 5 groups for analysis of data based on the number of years of work in the petrol pumps. Outdoor air analysis was also carried out. The FVC, FEV1 and PEF declined significantly with increasing years of work in petrol stations in both smokers and non-smokers. Smoking as an independent variable was found to affect the FEV1 significantly but not FVC or PEF. The FEF25-75 was found to be the most affected spirometric value with a significant reduction with increasing years of work. Smoking as such did not affect it. Oxides of nitrogen (NOx), suspended particulate matter (SPM) and particulate matter less than 10 microns (PM10) in outdoor air were higher than the national ambient air quality standards. Exposure to automobile exhaust and fuel vapour impairs lung function in a time-dependent manner. Cigarette smoking appears to accelerate the decline.
We present a case of allergic fungal sinusitis (AFS) in a 24 -year old man with history of left sided nasal obstruction and discharge since few years. Since few months he developed epiphora in the ...left eye associated with discomfort on eye movements. Patient was examined and CT with contrast was done. CT contrast showed an enhancing lesion in Left maxillary and ethmoid sinuses and erosion of the inferior bony wall of the orbit and medial wall of maxillary sinus. Though most patients of fungal sinusitis are immunocompromised but this patient was young male immunocompetent and made an unusual presentation with visual epiphora and painful eye movements. CT showed bony erosion of the Left inferior Bony wall of the Orbit and medial wall of Maxillary Sinus. After through examination and specific investigations, the patient was posted for surgery. We planed for Cald well –Luc’s Surgery and Endoscopic excision of the mass .Histological examination was reported as non malignant and microscopy showed Fungal Hyphae. After the surgery patient was discharged satisfactorily within couple of days and followed up regularly. Journal of College of Medical Sciences-Nepal,2012,Vol-8,No-1, 48-51 DOI: http://dx.doi.org/10.3126/jcmsn.v8i1.6826
Although hemangiomas are common in infancy and childhood, they are probably developmental abnormalities rather than true neoplasms. In present case we have treated a child aged 10 years with ...haemangioma of the right side of the Neck. After thorough investigation we posted this for intralesional infiltration of Sclerosing agent (Inj. Polidocanol 3%) in 1:3 dilution with normal saline. Approximately 2 ml Inj. Polidocanol diluted with saline was injected into the lesion. And the same procedure was repeated in three sittings after one week interval. The size and vascularity was reduced dramatically after single procedure. Patient was followed up after one and two months interval. There was no sign of any recurrence. This Procedure was chosen as it is cosmetically more acceptable, can be used for the haemangiomas at inaccessible areas where surgery is difficult, day care procedure and cost effective. Journal of College of Medical Sciences-Nepal,2012,Vol-8,No-1, 56-59 DOI: http://dx.doi.org/10.3126/jcmsn.v8i1.6828
Vasovagal syncope: an enigma Mohan, Latika; Lavania, A K
Journal of the Association of Physicians of India
52
Journal Article
Recenzirano
Syncope is a common clinical problem affecting 3.5% of the general population. About 40% of cases remain undiagnosed and 30% experience recurrent episodes. The article presents an update on the ...etiopathogenesis and theories of syncope. The pathophysiology of syncope remains elusive. Lewis introduced the term "vasovagal" implying therein that both vasodilatation and bradycardia were involved in the response. Individuals susceptible are unable to maintain adaptive neurocardiovascular responses to upright posture for prolonged periods of time. A complex hemodynamic response develops, with marked hypotension, bradycardia and a loss of consciousness. The "empty ventricle theory", first proposed by Sharpey - Schafer, widely accepted for several years, has been challenged and various other aspects of the vasovagal response have now been studied and implicated in contributing to the episode of unconsciousness. These include baroreflex dysfunction, neuro - endocrine responses, role of respiration and cerebrovascular dysfunction. An episode of syncope represents an episode of unconsciousness. Even a single episode of unconsciousness in the present day lifestyle is a source of distress to a patient, warranting a workup and diagnosis. The etiopathogenesis of the simple faint is complex and we may well be dealing with a constellation of responses and a more detailed classification than hitherto imagined.
Oxygen toxicity Chawla, Anuj; Lavania, AK
Medical Journal Armed Forces India/MJAFI,
04/2001, Letnik:
57, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Oxygen, the gas vital to sustain life, can also destroy it. It may become toxic at an elevated partial pressure, which may be the result of a rise in inspired oxygen concentration, an increase in ...environmental pressure or a combination of both. The toxicity tends to express itself most recognizably in one of several forms including central nervous system manifestations, pulmonary signs and symptoms and ocular effects, especially in premature infants. Other forms of toxicity should be expected in severe exposure but are difficult to detect and hence are not often considered important limitations for the use of oxygen. The onset and degree of the toxicity vary with the concentration of the gas used and the duration of exposure. Marked variations in individual susceptibility are found. Prevention of its occurrence and early detection of toxicity arc called for, the treatment being symptomatic.
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