Publications by authors named "R Shetty"

776 Publications

Fluid dynamics of droplet generation from corneal tear film during non-contact tonometry in the context of pathogen transmission.

Phys Fluids (1994) 2021 Sep 14;33(9):092109. Epub 2021 Sep 14.

Department of Mechanical Engineering, Indian Institute of Science, Bengaluru, KA 560012, India.

Noninvasive ocular diagnostics demonstrate a propensity for droplet generation and present a potential pathway of distribution for pathogens such as the severe acute respiratory syndrome coronavirus 2. High-speed images of the eye subjected to air puff tonometry (glaucoma detection) reveal three-dimensional, spatiotemporal interaction between the puff and tear film. The interaction finally leads to the rupture and breakup of the tear film culminating into sub-millimeter sized droplet projectiles traveling at speeds of 0.2 m/s. The calculated droplet spread radius ( 0.5 m) confirms the likelihood of the procedure to generate droplets that may disperse in air as well as splash on instruments, raising the potential of infection. We provide a detailed physical exposition of the entire procedure using high fidelity experiments and theoretical modeling. We conclude that air puff induced corneal deformation and subsequent capillary waves lead to flow instabilities (Rayleigh-Taylor, Rayleigh-Plateau) that lead to tear film ejection, expansion, stretching, and subsequent droplet formation.
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http://dx.doi.org/10.1063/5.0061956DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8450912PMC
September 2021

Reactivation of varicella zoster infection presenting as acute retinal necrosis post COVID 19 vaccination in an Asian Indian male.

Eur J Ophthalmol 2021 Sep 18:11206721211046485. Epub 2021 Sep 18.

Department of Cornea and Neurophthalmology, Narayana Nethralaya, Bengaluru, Karnataka, India.

Purpose: To present the clinical features of a rare case of varicella zoster infection following one dose of Coronavirus Disease 2019 (COVID-19) vaccination in an elderly Asian Indian male.

Methods: Retrospective observational case report.

Results: A 71-year-old gentleman presented to us with complaints of reduced vision associated with redness and pain in his right eye for 1 week. On examination he revealed a right eye pan uveitis picture with circumcorneal congestion, multiple fine keratic precipitates, anterior chamber cells and flare, vitritis and widespread areas of acute retinal necrosis. His left eye was within normal limits. Ten days prior to the presentation he had received the first dose of COVID-19 vaccine following which he had developed fever for 2 days that preceded the red eye. The patient's aqueous sample tested positive for varicella zoster virus (VZV) by nested polymerase chain reaction (PCR) method. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in reverse transcriptase polymerase chain reaction (RT-PCR) assay from the aqueous and also from the nasopharyngeal swab was negative.

Conclusion And Significance: To the best of our knowledge this is the earliest description of a case that has a viral reactivation following COVID-19 vaccination. Elderly people with pre-existing comorbidities, may be at a risk of both primary coronavirus infection and unconceivable risk of aberrant immune reactions leading to a different virus infection or reactivation need to be kept in mind. We present a possible link between SARS-CoV-2 virus vaccination and varicella zoster reactivation in this patient.
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http://dx.doi.org/10.1177/11206721211046485DOI Listing
September 2021

Abnormal B-cell development in TIMP deficient bone marrow.

Blood Adv 2021 Sep 9. Epub 2021 Sep 9.

Princess Margaret Cancer Centre/University Health Network, Toronto, ON, Canada, Torornto, Canada.

Bone marrow (BM) is the primary site of hematopoiesis and is responsible for a lifelong supply of all blood cell lineages. The process of hematopoiesis follows key intrinsic programs that also integrate instructive signals from the BM niche. First identified as an erythropoietin potentiating factor, tissue inhibitor of metalloproteinase (TIMP) protein family has expanded to 4 members and has widely come to be viewed as a classical regulator of tissue homeostasis. By virtue of metalloprotease inhibition, TIMPs not only regulate extracellular matrix turnover but also control growth factor bioavailability. The four mammalian TIMPs possess overlapping enzyme inhibition profiles and have never been studied for their cumulative role in hematopoiesis. Here, we show that TIMPs are critical for post-natal B lymphopoiesis in the BM. TIMP-deficient mice have defective B-cell development arising at the pro-B cell stage. Expression analysis of TIMPless hematopoietic cell subsets pointed to an altered B-cell program in the Lineage-c-Kit+Sca-1+ cell (LSK) fraction. Serial and competitive BM transplants identified a defect in TIMP- deficient HSPCs for B lymphopoiesis. In parallel, reverse BM transplants uncovered the extrinsic role of stromal TIMPs in pro- and pre-B cell development. TIMP-deficiency disrupted CXCL12 localization to LepR+ cells, and increased soluble CXCL12 within the BM niche. It also compromised the number and morphology of LepR+ cells. These data provide new evidence that TIMPs control the cellular and biochemical makeup of the BM niche along with influencing the LSK transcriptional program required for optimal B-lymphopoiesis.
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http://dx.doi.org/10.1182/bloodadvances.2020004101DOI Listing
September 2021

Optical coherence tomography angiography (OCTA) of retinal vasculature in patients with post fever retinitis: a qualitative and quantitative analysis.

Sci Rep 2021 Sep 3;11(1):17647. Epub 2021 Sep 3.

Department of Cornea and Refractive Surgery, Narayana Nethralaya, 121/C. Chord Road, Bangalore, Karnataka, 560010, India.

Post fever retinitis is a heterogenous entity that is seen 2-4 weeks after a systemic febrile illness in an immunocompetent individual. It may occur following bacterial, viruses, or protozoal infection. Optical coherence angiography (OCTA) is a newer non-invasive modality that is an alternative to fundus fluorescein angiography to image the retinal microvasculature. We hereby describe the vascular changes during the acute phase of post fever retinitis on OCTA. Imaging on OCTA was done for all patients with post fever retinitis at presentation with 3 × 3 mm and 8 × 8 mm scans centred on the macula and corresponding enface optical coherence tomography (OCT) scans obtained. A qualitative and quantitative analysis was done for all images. 46 eyes of 33 patients were included in the study. Salient features noted were changes in the superficial (SCP) and deep capillary plexus (DCP) with capillary rarefaction and irregularity of larger vessels in the SCP. The DCP had more capillary rarefaction when compared to the SCP. The foveal avascular zone (FAZ) was altered with an irregular perifoveal network. Our series of post fever retinitis describes the salient vascular features on OCTA. Although the presumed aetiology was different in all our patients, they developed similar changes on OCTA. While OCTA is not useful if there is gross macular oedema, the altered FAZ can be indicative of macular ischemia.
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http://dx.doi.org/10.1038/s41598-021-96715-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8417288PMC
September 2021

A Comparative Evaluation of Abrasion Resistance of Three Commercially Available Type IV Dental Stone, Dried using Three Different Drying Techniques - An Study.

J Pharm Bioallied Sci 2021 Jun 5;13(Suppl 1):S580-S585. Epub 2021 Jun 5.

Department of Pedodontics, Sree Mookambika Institute of Dental Science, Kanyakumari, Tamil Nadu, India.

Background: The microwave technique of drying dental stone to achieve improved hardness and strength has been suggested in recent years. However, its effect on the wear properties of dental stone has not been thoroughly examined.

Aim: The present study was conducted to determine the abrasion resistance of three commercially available Type IV dental stones using three different drying techniques.

Materials And Methods: A total of 180 samples were prepared from 3 Type IV dental stones; namely Eliterock, Zhermack (Italy), Kalrock, Kalabhai industries (India), and Gyprock (Rajkot, India). Samples were subjected to drying in open air for 2 h, hot air oven at a temp of 230°C for 1 h and microwave oven for 5 min at 900Watts. Abrasion resistance was determined using a customized metallic abrasion resistance tester.

Results: Microwave oven drying produced samples with increased abrasion resistance values when compared to samples dried in hot air oven and air-dried specimens. Eliterock showed significantly higher mean abrasion resistance values followed by Kalrock and Gyprock.

Conclusion: Drying type IV dental stone in a microwave oven at 900W for 5 min increased the abrasion resistance within short time.
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http://dx.doi.org/10.4103/jpbs.JPBS_538_20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8375857PMC
June 2021
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