Role of membrane associated serine esterase in the activation of phospholipase A2 by calcium ionophore (A23187) in pulmonary arterial smooth muscle cells

Exposure of rabbit pulmonary arterial smooth muscle cells to 10 M of the calcium ionophore A23187 dramatically stimulates cell membrane-associated phospholipase A₂ activity and arachidonic acid release. In addition, A23187 also enhances cell membrane-associated serine esterase activity. Serine esterase inhibitors phenylmethylsulfonylfuoride and diisopropyl fluorophosphate prevent the increase in serine esterase and phospholipase A₂ activities and arachidonic acid release caused by A23187. A23187 still stimulated serine esterase and phospholipase A₂ activities and arachidonic acid release in cells pretreated with nominal Ca²⁺ free buffer. Treatment of the cell membrane with A23187 does not cause any appreciable change in serine esterase and phospholipase A₂ activities. Pretreatment of the cells with actinomycin D or cycloheximide did not prevent the increase in the cell membrane associated serine esterase and phospholipase A₂ activities, and arachidonic acid release caused by A23187. These results suggest that (i) a membrane-associated serine esterase plays an important role in stimulating the smooth muscle cell membrane associated phospholipase A₂ activity (ii) in addition to the presence of extracellular Ca²⁺, release of Ca²⁺ from intracellular storage site(s) by A23187 also appears to play a role in stimulating the cell membrane-associated serine esterase and phospholipase A₂ activities, and (iii) the increase in the cell membrane-associated serine esterase and phospholipase A₂ activities does not appear to require new RNA or protein synthesis.Abbreviations A23187 calcium ionophore - AA arachidonic acid - PMSF phenylmethyl sulfonylfuoride - DFP diisopropyl-fluorophosphate - DMEM Dulbecco's modified Eagles medium - FCS fetal calf serum - PBS phosphate buffered saline - HBPS Hank's buffered physiological saline - PLA₂ phospholipase A₂     

Improved photoluminescence stability and defect passivation in SbBr3 post-treated CsPbBr3 quantum dots under ambient conditions

Inorganic cesium lead halide perovskites have evoked wide popularity because of their excellent optoelectronic properties, high photoluminescence (PL) quantum yield (PLQY), and narrowband emission. Here, cesium lead bromide (CsPbBr₃) quantum dots (QDs) were synthesized via the ligand-assisted re-precipitation method. Post-synthesis treatment of CsPbBr₃ QDs using antimony tribromide improved the PL stability and optoelectronic properties of the QDs. In addition, the PLQY of the post-treated sample was enhanced to 91% via post-treatment, and the luminescence observed was maintained for 8 days. The post-synthesis treatment ensured defect passivation and improved the stability of CsPbBr₃ perovskite QDs. High-resolution transmission electron microscopy revealed the presence of more ordered, uniform-sized CsPbBr₃ QDs after post-synthesis treatment, and the uniformity of the sample improved as the day passed. The formation of a mixed crystal phase was observed from X-ray diffraction in both as-synthesized, as well as post-treated QDs samples with the possibility of a polycrystalline nature in the post-treated CsPbBr₃ QDs as per the selected area electron diffraction pattern. The X-ray photoelectron spectroscopy spectra confirmed the presence of antimony and the possibility of defect passivation in the post-treated samples. These QDs can act as potential candidates in various optoelectronic applications such as photodetectors and light-emitting diodes due to their high PLQY and longer lifetime.     

Evaluation of the toxicity of different phytoextracts of Ocimum basilicum against Anopheles stephensi and Culex quinquefasciatus

The larvicidal effect of the crude carbon tetrachloride, methanol and petroleum ether leaf extracts of a widely grown medicinal plant, Ocimum basilicum, against Anopheles stephensi and Culex quinquefasciatus was evaluated. Petroleum ether extract was found to be the most effective against the larvae of both mosquitoes, with LC₅₀ values of 8.29, 4.57; 87.68, 47.25 ppm and LC₉₀ values of 10.06, 6.06; 129.32, 65.58 ppm against A. stephensi and C. quinquefasciatus being observed after 24 and 48 h of treatment, respectively. The efficacy of petroleum ether was followed by that of the carbon tetrachloride and methanol extracts, which had LC₅₀ values of 268.61, 143.85; 446.61, 384.84 ppm and LC₉₀ values of 641.23, 507.80; 923.60, 887.00 ppm against A. stephensi after 24 and 48 h, respectively, and LC₅₀ values of 24.14, 17.02; 63.48, 53.77 ppm and LC₉₀ values of 295.38, 204.23; 689.71, 388.87 ppm against C. quinquefasciatus after 24 and 48 h of treatment, respectively. These extracts are highly toxic against mosquito larvae from a range of species; therefore, they may be useful for the management of mosquito larvae to control vector borne diseases.     

Stability analysis and optimal control of an SIR epidemic model with vaccination

This paper focuses on the study of a nonlinear mathematical SIR epidemic model with a vaccination program. We have discussed the existence and the stability of both the disease free and endemic equilibrium. Vaccine induced reproduction number is determined and the impact of vaccination in reducing the vaccine induced reproduction number is discussed. Then to achieve control of the disease, a control problem is formulated and it is shown that an optimal control exists for our model. The optimality system is derived and solved numerically using the Runge-Kutta fourth order procedure.     

Cation Substitution of Solution‐Processed Cu2ZnSnS4 Thin Film Solar Cell with over 9% Efficiency

To alleviate the limitations of pure sulfide Cu₂ZnSnS₄ (CZTS) thin film, such as band gaps adjustment, antisite defects, secondary phase and microstructure, Cadmium is introduced into CZTS thin film to replace Zn partially to form Cu₂Zn_1?xCd_xSnS₄ (CZCTS) thin film by low‐cost sol–gel method. It is demonstrated that the band gaps and crystal structure of CZCTS thin films are affected by the change in Zn/Cd ratio. In addition, the ZnS secondary phase can be decreased and the grain sizes can be improved to some degree by partial replacement of Zn with Cd in CZCTS thin film. The power conversion efficiency of CZTS solar cell device is enhanced significantly from 5.30% to 9.24% (active area efficiency 9.82%) with appropriate ratio of Zn/Cd. The variation of device parameter as a function of Zn/Cd ratio may be attributed to the change in electronic structure of the bulk CZCTS thin film (i.e., phase change from kesterite to stannite), which in turn affects the band alignment at the CZCTS/buffer interface and the charge separation at this interface.     

Targets of oxidative stress in cardiovascular system

Although oxidants such as superoxide (O₂.^-) and hydrogen peroxide (H₂O₂) play a role in host-mediated destruction of foreign pathogens yet excessive generation of oxidants may lead to a variety of pathological complications in the cardiovascular system. An important mechanism by which oxidants cause dysfunction of the cardiovascular system appears to be due to the increase in intracellular free Ca²⁺ concentration. Oxidants cause cellular Ca²⁺ mobilization by modulating activities of a variety of regulators such as Na⁺/H⁺ and Na⁺/Ca²⁺ exchangers, Na⁺/K⁺ ATPase and Ca²⁺ ATPase and Ca²⁺ channels that are associated with Ca²⁺ transport in the plasma membrane and the sarco(endo)plasmic reticular membrane of myocardial cells. Recent research have suggested that the increase in Ca²⁺ level by oxidants plays a pivotal role in indicing several protein kinases such as protein kinase C, tyrosine kinase and mitogen activated protein kinases. Oxindant-mediated alteration of different signal transduction systems and their interations eventually regulate a variety of pathological conditoins such as atherosclerosis, apoptosis and necrosis in the myocardium     

Isolation,molecular characterization and antibiotic resistance of Shiga Toxin–Producing Escherichia coli (STEC) from buffalo in India

In total, 363 Escherichia coli were isolated from 165 faecal samples of healthy buffaloes in West Bengal, India. Twenty‐four of these isolates (6·61%) were found to carry at least one gene characteristic for Shiga toxin–producing Escherichia coli (STEC). These STEC strains belonged to 13 different O‐serogroups. The stx₁ gene was present in 23 (95·8%) of total STEC isolates, whereas 20 (83·3%) STEC isolates carried the gene stx_2. Twelve strains of E. coli (50% of total STEC isolates) possessed enterohaemolysin (ehxA) gene in combination with others. Fourteen (58·33%) isolates found to possess saa gene. However, no E. coli was detected harbouring gene for intimin protein (eaeA). Of 23 stx₁‐positive isolates, seven (30·43%) were positive for genes of the stx_1C subtype. Of the 20 isolates with the stx₂ gene, 25% (5/20) possessed stx_2C and 10% (2/20) possessed stx_2d gene. The phylogenetic analysis after RAPD of STEC strains revealed six major clusters. The isolated STEC strains were resistant most frequently to erythromycin (95·83%), cephalothin (62·5%), amikacin (54·17%), kanamycin (45·83%) and gentamicin (41·67%) group of antibiotics. No ESBL‐producing (bla_CTXM, bla_TEM, bla_SHV) or quinolone resistance gene (qnrA) was detected in the STEC isolates.

Significance and Impact of the Study

The buffaloes from different districts of West Bengal, India, are important reservoir of multidrug‐resistant Shiga toxin–producing Escherichia coli (STEC). India is home to more than 56% of world buffalo population, traditionally raised by farmers. So, there is a major risk of transmission of STEC among the human population of this part of the globe. However, there is no prevalence study of STEC from healthy or diarrhoeic buffalo in India. The present study reports for the first time in India about isolation, molecular characterization and antibiotic resistance pattern of STEC in healthy buffaloes.     

Ultrafast electron transfer in the recognition of different DNA sequences by a DNA-binding protein with different dynamical conformations

Ultrafast electron transfer (ET) phenomenon in protein and protein–DNA complex is very much crucial and often leads to the regulation of various kinds of redox reactions in biological system. Although, the conformation of the protein in protein–DNA complex is concluded to play the key role in the ET process, till date very little evidences exist in the literature. λ-repressor–operator DNA interaction, particularly O_R1 and O_R2, is a key component of the λ-genetic switch and is a model system for understanding the chemical principles of the conformation-dependent ET reaction, governed by differential protein dynamics upon binding with different DNA target sequences. Here, we have explored the photoinduced electron transfer from the tryptophan moieties of the protein λ-repressor to two operators DNA of different sequences (O_R1 and O_R2) using picosecond-resolved fluorescence spectroscopy. The enhanced flexibility and different conformation of the C-terminal domain of the repressor upon complexation with O_R1 DNA compared to O_R2 DNA are found to have pronounced effect on the rate of ET. We have also observed the ET phenomenon from a dansyl chromophore, bound to the lysine residue, distal from the DNA-binding domain of the protein to the operator DNA with a specific excitation at 299?nm wavelength. The altered ET dynamics as a consequence of differential protein conformation upon specific DNA sequence recognition may have tremendous biological implications.     

Serogroup distribution and virulence characteristics of sorbitol‐negative Escherichia coli from food and cattle stool

Aims: To (i) study the serogroup distribution and virulence characteristics of non‐sorbitol‐fermenting Escherichia coli isolates from foods of animal origin and cattle faeces and (ii) re‐examine the true sorbitol and β‐d ‐glucuronidase (GUD) reactions of sorbitol‐negative (Sor^?) strains from MacConkey sorbitol agar (SMAC) to assess their phenotypic similarity with E. coli O157. Methods and Results: One hundred and thirty Sor^?E. coli were isolated from 556 food samples and 177 cattle stool samples using cefixime tellurite–supplemented SMAC (CT‐SMAC) and chromogenic HiCrome MS.O157 agar respectively. Based on typing of somatic antigen, the isolates were classified into 38 serogroups. PCR results identified about 40% strains, belonging to O5, O8, O20, O28, O48, O60, O78, O82, O84, O101, O110, O123, O132, O156, O157, O‐rough and OUT as Shiga toxigenic. Majority of O5, O84, O101, O105, O123, O157, O‐rough and OUT strains were enterohaemolytic. Further, 39·2% and 63·1% of Sor^? isolates from CT‐SMAC fermented sorbitol in phenol red broth and hydrolysed 4‐methylumbelliferyl‐β‐d ‐glucuronide (MUG) respectively. Members of serogroups O5, O28, O32, O81, O82, O84, O101, O‐rough lacked both the sorbitol fermentation (broth test) and GUD activity and might create confusion in phenotypic identification of E. coli O157. Conclusions: Sor^?E. coli isolates from raw meat, milk, shrimp and cattle stool belonged to 38 serogroups, with E. coli O157 constituting only 14·6% of the isolates. Many of these nonclinical Sor^? strains were potentially pathogenic. Nearly 39% of these Sor^?E. coli from CT‐SMAC fermented sorbitol in broth, indicating the need for confirmation of sorbitol reaction in broth. Significance and Impacts of the Study: Classical sorbitol utilization and GUD tests are not likely definitive tests for E. coli O157. Further improvement of differential media based on these phenotypic properties is necessary for detection of pathogenic serotypes from foods and environmental samples.     

Occurrence, virulence characteristics and antimicrobial resistance of Escherichia coli O157 in slaughtered cattle and diarrhoeic calves in West Bengal, India

AIMS: (i) To study the occurrence of Escherichia coli serotype O157 in cattle stool in West Bengal, India, and (ii) the virulence properties and antimicrobial resistance of the E. coli isolates. METHODS AND RESULTS: Following enrichment in modified EC broth and plating onto HiCrome MS.O157 agar, a total of 14 strains of E. coli serotype O157 was isolated from faecal samples from two (2.04%) slaughtered cattle and six (7.59%) diarrhoeic calves. By multiplex PCR, Shiga toxin genes were detected in all the isolates. The enterohaemolysin phenotype was found in all, but one strain. Among 14 strains, ten were resistant to at least one of the antimicrobial agents tested. Multiple antibiotic resistance was frequent. CONCLUSIONS: The study showed that occurrence of Shiga toxin-producing and multiple antibiotic-resistant E. coli O157 among cattle population in this region of India is significant. SIGNIFICANCE AND IMPACT OF THE STUDY: Considering routine human contacts with cattle, a large human population in this region may be at risk for exposure to Shiga toxin-producing E. coli O157.