Subendu Sarkar

Cloud Characteristics and Cloud Attenuation in Millimeter Wave and Microwave Frequency Bands for Satellite and Remote Sensing Applications over a Northern Indian Tropical Station

Microwave and millimeter wave frequency bands are in demand for requirement of more channels in radio communication systems. It has also been recognized that microwave and millimeterwave frequency radiometers on board satellites as promising tools for remote sensing.The frequency more than 10 GHz is affected by rain and cloud. Though the effects of rain on radiowave is more than cloud but the occurence of cloud is more than rain. Cloud has been found to occur for weeks together over this part of the world. It is therefore essential to study cloud morphology over different geographical region.In this paper, an attempt has been made to the cloud occurrences over an Indian tropical station, Delhi (28.35°N, 77.12°E) observed during different months and daytime and nighttime. It is seen that low clouds occurrence over Delhi is very significant and particularly during July, August and September. The specific attenuation of radiowave due to clouds at various frequencies 10 GHz, 20 GHz, 50 GHz and 100 GHz has been deduced. The specific attenuation of radio wave due to cloud at 10 GHz varies from 0.0608 dB/km to 0.1190 dB/km while at 100 GHz the specific attenuation varies from 6.8460 dB/km to 11.9810 dB/km

Vitamin D regulates the production of vascular endothelial growth factor: A triggering cause in the pathogenesis of rheumatic heart disease?

Rheumatic heart disease (RHD) remains a major cause of cardiac related mortality and morbidity in the developing countries due to poor diagnosis and lack of proper therapeutics. The definite reason of heart valve injury during RHD is poorly understood. Valvular endothelial cells play an important role in pathogenesis of different cardiovascular diseases. Besides, the regulation of vitamin D (calciferol) and VEGF (vascular endothelial growth factor) results in the functional changes in endothelial cells. However, the crosstalk between vitamin D and VEGF in the pathogenesis of RHD is not yet unfurled. Evidences in the concerned fields are documented by searching through Google Scholar and Pubmed. Literature based survey has revealed that vascular endothelium, especially endothelial cells play important roles in valvular remodelling during cardiovascular diseases. Endothelial cell dysfunction leads to heart valve remodelling, which furthermore initiates the pathogenesis of valvular heart disease. Vitamin D has the potential to maintain the concentration of VEGF in the circulation and induce the function of endothelial cells. Hence, we hypothesize that vitamin D and VEGF homeostasis can alter the function of endothelial cells, which may subsequently trigger the valvular remodelling or even damage of heart valves during the progression of RHD pathogenesis. Our hypothesis shed light on the evidence based knowledge translation of plausible cellular phenomena due to vitamin D/VEGF homeostasis during valvular vandalism in RHD.

Identification of orcinol reactive substance in pleural fluid cell lysate—A new parameter for classification of pleural effusion

BACKGROUND Cell-free DNA is observed to be more in exudative pleural effusions. Based on this fact development of a clinical chemistry test for classification of pleural effusion will require DNA extraction followed by PCR amplification and electrophoresis. These procedures may not be cost effective for the purpose for classification of pleural effusion as already established parameters are popular for the purpose which can be estimated by comparatively low cost colorimetric procedures. Therefore development of a simple colorimetric test for the classification of pleural fluid based on nucleic acid identification test can be attempted. The aim of this work is to develop such colorimetric test for classification of pleural effusion using only pleural fluid sample. METHODS Cell pellet is obtained from 5 ml pleural fluid which is lysed and subjected to DNA extraction, followed by identification under UV-transilluminator after electrophoresis and orcinol and diphenylamine reaction. RESULT Exudates show extractable DNA from 5 ml biofluid (n=52) which are not observed from transudate (n=32). Orcinol reaction is significantly positive in exudates (n=52) compared to the transudates (n=32). Diphenylamine test cannot differentiate exudate from transudate. CONCLUSION Orcinol reaction of cell lysate obtained from pleural fluid can classify pleural fluid sample into exudate or transudate.

A drop of hydrogen peroxide can differentiate exudative pleural effusion from transudate — development of a bedside screening test

BACKGROUND There is no bedside test to classify pleural fluid as exudate or transudate. The aim of the present study is to develop such a test. METHODS We analyzed the Lights criteria parameters from bloodless pleural fluid and classified the biofluid as exudate or transudate and also estimated some parameters of oxidative stress in the biofluid by established spectrophotometric procedure. Two hundred microliters of sample was taken and added with 10 microl of 30% hydrogen peroxide followed by inspection of the sample for appearance of bubbles. RESULT All exudative fluids (n=52) have shown appearance of profuse bubbles within 1 min of addition of hydrogen peroxide along with significantly more catalase activity compared to transudate. All transudative fluids (n=32) have not shown bubble formation within 1 min after addition of hydrogen peroxide. The exudate does not show bubble formation if supplemented with catalase inhibitors. Blood mixed transudate have shown profuse bubble formation after addition of hydrogen peroxide. CONCLUSION In the case of blood uncontaminated pleural fluid, this newly developed protocols sensitivity and specificity will be equivalent to Lights criteria probably with more advantage as by this procedure transport of the sample to the clinical laboratory is not required due to its inherent simplicity.

Virulence determinants in enteroaggregative Escherichia coli from North India and their interaction in in vitro organ culture system.

Enteroaggregative Escherichia coli (EAEC) is an important diarrhoeal pathogen causing diseases in multiple epidemiological and clinical settings. In developing countries like India, diarrhoeal diseases are one of the major killers among paediatric population and oddly, few studies are available from Indian paediatric population on the variability of EAEC virulence genes. In this study, we examined the distribution of plasmid and chromosomal-encoded virulence determinants in EAEC isolates, and analysed cytokines response generated against EAEC with specific aggregative adherence fimbriae (AAF) type in duodenal biopsies using in vitro organ culture (IVOC) mimicking in vivo conditions. Different virulence marker combinations among strains were reflected as a function of specific adhesins signifying EAEC heterogeneity. fis gene emerged as an important genetic marker apart from aggA and aap Further, EAEC infection in IVOC showed upregulation of IL-8, IL-1β, IL-6, TNF-α and TLR-5 expression. EAEC with AAFII induced significant TLR-5 and IL-8 response, conceivably owing to more pathogenicity markers. This study sheds light on the pattern of EAEC pathotypes prevalent in North Indian paediatric population and highlights the presence of unique virulence combinations in pathogenic strains. Thus, evident diversity in EAEC virulence and multifaceted bacteria-host crosstalk can provide useful insights for the strategic management of diarrhoeal diseases in India, where diarrhoeal outbreaks are more frequent.

Association of rheumatic fever & rheumatic heart disease with plausible early & late-stage disease markers

Background & objectives: Rheumatic fever (RF) and rheumatic heart disease (RHD) are the autoimmune sequelae caused by Group A Streptococcus. RHD still remains a major concern in the developing countries due to its poor diagnosis, lack of vaccines and social awareness among population. This study was aimed to identify the plausible early- and late-stage disease markers associated with RF/RHD. Methods: A total of 84 patients with confirmed pharyngitis (n=18), RF (n=23) and RHD (n=43) were included in the comparative analysis of different factors involved in host-pathogen interaction during RF/RHD pathogenesis. Results: This study revealed high titre of serum antistreptolysin O (ASO) antibody in pharyngitis compared to RF and RHD patients, whereas procollagen type 1 C-peptide (PICP) level was elevated in RHD which showed an inverse correlation with serum ASO titre. The significant elevation of serum anti-peptide associated with RF (PARF) antibody in RF patients was correlated as a probable stage-specific determinant. In addition, pro-inflammatory cytokine profile revealed high levels of interleukin-12 (IL-12)/IL-23p40, IL-17A in RF, whereas IL-6 concentration was higher in RHD compared to healthy controls. Interpretation & conclusions: The overall assessment of the factors/disease markers involved in host-pathogen interaction in RF/RHD may be suggestive of plausible disease marker in different groups of patients. Further studies with larger sample need to be done to better understand RF/RHD pathogenesis.

Anti-endothelial cell antibody rich sera from rheumatic heart disease patients induces proinflammatory phenotype and methylation alteration in endothelial cells

Rheumatic heart disease (RHD) is a major cause of cardiovascular morbidity and mortality in developing nations like India. RHD commonly affects the mitral valve which is lined by a single layer of endothelial cells (ECs). The role of ECs in mitral valve damage during RHD is not well elucidated. In here, anti-endothelial cell antibody from RHD patients has been used to stimulate the ECs (HUVECs and HMVECs). ECs proinflammatory phenotype with increased expression of TNFα, IL-6, IL-8, IFNγ, IL-1β, ICAM1, VCAM1, E-selectin, laminin B, and vimentin was documented in both ECs. The promoter hypomethylation of various key inflammatory cytokines (TNFα, IL-6, and IL-8), integrin (ICAM1) associated with leukocyte transendothelial migration, and extracellular matrix genes (vimentin, and laminin) were also observed. Further, the in-vitro data was in accordance with ex-vivo observations which correlated significantly with the etiological factors such as smoking, socioeconomic status, and housing. Thus, the study sheds light on the role of ECs in RHD which is a step forward in the elucidation of disease pathogenesis.

Identification of unique proteins in vitreous fluid of patients with noninfectious uveitis

Uveitis is a cause for concern in the developing countries like India. Its poor diagnosis and lack of proper therapeutics often cause blindness in children and young adults. Moreover, the exact mechanism of pathogenesis of different types of uveitis is still elusive. Modern proteomic techniques are found to be advantageous for an in‐depth understanding of the ocular physiology using proteomic diversity. Our aim was to identify unique proteins involved in the pathogenesis of autoimmune or noninfectious uveitis.

Development of a point of care testing tool to classify peritoneal effusion as exudate and transudate

BACKGROUND Recently we developed a bedside test to classify pleural effusion into exudate and transudate but point of care classification of peritoneal effusion is yet not published. METHODS We analyzed the Boyers criteria parameters from bloodless peritoneal fluid and classified the biofluid as exudate or transudate and also estimated some parameters of oxidative stress in the biofluid by established spectrophotometric procedure. Two hundred microliters of sample was used and 10 μl of 30% hydrogen peroxide was added, followed by inspection of the sample for the appearance of bubbles. RESULTS All exudative ascitic fluids (n=50) have shown the appearance of profuse bubbles within 1 min addition of hydrogen peroxide along with significantly more catalase activity compared to transudate. All transudative ascitic fluids (n=50) have not shown bubble formation within 1 min after the addition of hydrogen peroxide. The exudate does not show bubble formation if added with catalase inhibitors prior to the addition of hydrogen peroxide. Blood mixed transudate have shown profuse bubble formation after the addition of hydrogen peroxide. CONCLUSION The hydrogen peroxide bubbling reaction has the potential to be developed as a point of care test to classify peritoneal fluid as exudate or transudate.