Vector biology of dengue & chikungunya viruses.
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Aedes↗
Biomedical subjects
P Yadav
Publications and source records attributed to P Yadav.
From alcohols to sugars-how does the reactivity of alpha-hydroxyalkyl radicals change with structure? A quantitative examination by pulse radiolysis.
Rate constants are reported for the 1-electron reduction of the azo dye Orange II in water (pH 7.0) by 10 different alpha-hydroxy radicals. The radicals were created by pulse radiolysis of aqueous solutions of the corresponding alcohol/sugar. The rate constants varied from 1 x 10(8) to 2.7 x 10(9) mol(-1) dm(3) s(-1) and radicals with beta-hydroxy groups had the lowest rate constant. The reaction was found to be controlled by the reduction potentials of the radicals, with steric influences having little effects. Good fits of the data were obtained using the Marcus equation with lambda =140 kJ/mol.
Letter↗
Effect of temperature and insecticide stresses on Aedes aegypti larvae and their influence on the susceptibility of mosquitoes to dengue-2 virus.
Two major factors, higher temperatures and the application of insecticides, can drastically alter the genetic structure of a vector mosquito population. Due to these two stresses, the majority of the population gets wiped out, but the ones that withstand the stress and survive are likely to pass on survivability, and have an altered physiology. Our study shows that exposures to higher temperatures and DDT during the larval stage affects their susceptibility as adult mosquitoes to the DEN-2 virus. The overall transcription and translation status of heat shock protein (Hsp70) in virus high- and low-susceptible was the same as that in other batches. In the case of a DDT-resistant (R-7) strain two bands were obtained during RT-PCRs after heat shock. These two alleles were obtained only with HY-1 in which R-7 males were used for the crosses, suggesting that the second allele is probably male sex linked. The higher expression of Hsp70 may provide DDT-resistant strains a better chance of survival high temperature environments, particularly in homozygotes and hybrids. It was also interesting to note that these strains have a significantly lower susceptibility to the virus. Wide-spread DDT-resistance and a rise in temperature above the average temperature during summer may result in a population with a low susceptibility to the virus. Several families of heat shock proteins are known to be expressed in mosquitoes, and may have a cumulative role in determining susceptibility to the virus, which itself is governed by several genes.
Animals↗
Effect of temperature stress on immature stages and susceptibility of Aedes aegypti mosquitoes to chikungunya virus.
A high temperature stress of 44.5 degrees C for 10 minutes on the larval stages was found to affect the susceptibility of adult Aedes aegypti mosquitoes to chikungunya virus. At this temperature, the mortality of the mosquito larvae was found to be approximately 95%, whereas a temperature greater than 45 degrees C for 10 minutes was found to be lethal. A temperature tolerant (TT) strain was developed by exposing the larvae to a temperature of 44.5 degrees C for 10 minutes at every generation for five generations. This strain was established to determine whether increase in the susceptibility was due to any selection pressure of higher temperature or to the influence of other intrinsic factors such as expression of immunoresponsive (IR) genes. Other studies on these mosquito strains showed that when maintained at 28 +/- 1 degrees C, there was no difference in the larval duration and mortality in the immature stages, but the mean survival of female mosquitoes in the TT strain was 5-6 days longer. Conversely, when mosquitoes were maintained throughout at 37 degrees C the mean survival of the mosquitoes decreased drastically in both strains, but the mean survival of females in the TT strain was 5-6 days longer compared with the unstressed controls. This increases the probability of at least one more blood meal. Fecundity of the TT strain was found to be lower than that of the control mosquitoes. Data suggest that expression of certain IR genes was affected by the heat shock. Some of these genes were up-regulated and down-regulated, which may have affected the susceptibility of mosquitoes to the virus. Although there was some selection in the temperature-tolerant individuals in the TT strain, when stressed by heat they showed expression of IR genes in a pattern similar to that in the normal controls. It appears that an increase in temperature above the average temperature of an area might help increase the proportion of virus-susceptible mosquitoes in the population. Such an increase in temperature in an endemic area would not only enhance the selection of temperature-tolerant individuals in a population having more longevity, but would also affect both intrinsic and extrinsic factors by reducing the extrinsic incubation period and increasing susceptibility of mosquitoes to viruses due to affected expression of IR genes.
Aedes↗
Isolation of bovine viral diarrhea virus 1, a pestivirus from autopsied lamb specimen from Tamil Nadu, India.
An epizootic of febrile illness among the Madras red breed of sheep had occurred in 1994 in Verrapuram, Chennai, India. The epizootic was suspected as Rift Valley fever (RVF)-like sickness based on clinical features. However, its etiological agent could neither be isolated nor implicated conclusively. During the post-epizootic period a male lamb died of similar clinical features and the spleen was immediately collected. Inoculation of spleen suspension in infant mouse brain yielded a virus that was serially passaged in infant mice and rhabdomyosarcoma (RD) cells. Electron microscopic observations revealed virus particles resembling flaviviruses. RT-PCR performed on extracted total RNA from infected cells and mouse brains with flavivirus-specific or RVF-specific primers gave negative results. However, an amplicon of 280 bp was obtained with pestivirus-specific primers from the 5'-UTR. Further, a nested PCR yielded a product of 157 bp. Nucleotide sequencing of the 157 bp product showed 100% homology to BVDV-1. Western blot analysis with a flavivirus envelope protein-specific MAb revealed three proteins of 33 K, 45 K and 55 K. Further studies suggested that the 33 K and 55 K proteins were glycosylated. This is the first report of isolation of BVDV-1 from a lamb in India.
Animals↗
Experimental transmission of Chikungunya virus by Anopheles stephensi mosquitoes.
The Ades aegypti mosquito has been considered the principal vector of Chikungunya (CHIK) virus. As CHIK epidemics usually occur in urban regions and Anopheles stephensi is another highly endophilic and anthropophilic mosquito, there is a very high probability of this mosquito to feed on CHIK virus-infected patients, to pick up and transmit the virus. Therefore the present study was conducted to test the CHIK virus transmission capability for the A. stephensi mosquito. The obtained results showed that this mosquito species is capable of transmitting CHIK virus. It is surmised that during any epidemic of febrile illness CHIK virus isolation attempts should also be made from this mosquito species.
Alphavirus Infections↗
Genotyping of Chikungunya virus isolates from India during 1963-2000 by reverse transcription-polymerase chain reaction.
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Alphavirus Infections↗
Enhanced esterase activity in salivary gland and midgut of Aedes aegypti mosquito infected with dengue-2 virus.
Mosquitoes were infected by intrathoracic inoculation. About 95% head squashes were positive for dengue virus antigen on the 15th post infection day (PID). Esterase activity was determined in the homogenates prepared from the salivary glands and midguts on different PIDs of dengue virus inoculated and control mosquitoes showed that it was consistently higher in the virus-infected batches.
Aedes↗
Negative feedback on the effects of stem cell factor on hematopoiesis is partly mediated through neutral endopeptidase activity on substance P: a combined functional and proteomic study.
Hematopoietic regulation is a complex but dynamic process regulated by intercellular and intracellular interactions within the bone marrow (BM) microenvironment. Through neurokinin-1 (NK-1) and NK-2 receptors, peptides (eg, substance P [SP]) encoded by the preprotachykinin-I gene mediate distinct hematopoietic effects. Cytokines, associated with hematopoietic stimulation, and SP regulate the expression of each other in BM mesenchymal and immune cells. Neutral endopeptidase (NEP) uses SP as a substrate to produce SP(1-4), which inhibits the proliferation of matured myeloid progenitor. This study determines whether the degradation of SP to SP(1-4) by endogenous NEP in BM stroma could be a feedback on hematopoietic stimulation by stem cell factor (SCF). SP(1-4) induced the production of transforming growth factor (TGF)-beta and tumor necrosis factor-alpha in BM stroma. TGF-beta production accounted for part of the inhibitory effects by SP(1-4) on the proliferation of early (granulocyte-macrophage colony-forming units) and late (long-term culture-initiating cells) hematopoietic progenitors. Enzyme-linked immunosorbent assays and/or protein-chip arrays indicated a timeline change of SP to SP(1-4) in BM stroma stimulated with SCF, which correlated with increase in NEP messenger RNA. Since SP and its fragment, SP(1-4), interact with the same receptor to mediate opposing hematopoietic effects, 2 interactive studies were done to understand the dual responses of NK-1: (1) a 3-dimensional molecular model of NK-1 and SP and (2) screening of a random dodecapeptide library for SP(1-4) interacting sites. The effects of SP(1-4) on hematopoietic progenitors and the timeline change of SP to SP(1-4), together with the 3-dimensional model, provide a partial explanation for the feedback on the stimulatory effects of SCF and SP on hematopoiesis.
Binding Sites↗
Mimicry between neurokinin-1 and fibronectin may explain the transport and stability of increased substance P immunoreactivity in patients with bone marrow fibrosis.
Bone marrow (BM) fibrosis may occur in myeloproliferative diseases, lymphoma, myelodysplastic syndrome, myeloma, and infectious diseases. In this study, the role of substance P (SP), a peptide with pleiotropic functions, was examined. Some of its functions-angiogenesis, fibroblast proliferation, and stimulation of BM progenitors-are amenable to inducing BM fibrosis. Indeed, a significant increase was found in SP-immunoreactivity (SP-IR) in the sera of patients with BM fibrosis (n = 44) compared with the sera of patients with hematologic disorders and no histologic evidence of fibrosis (n = 46) (140 +/-12 vs 18 +/-3; P <.01). Immunoprecipitation of sera SP indicated that this peptide exists in the form of a complex with other molecule(s). It was, therefore, hypothesized that SP might be complexed with NK-1, its natural receptor, or with a molecule homologous to NK-1. To address this, 3 cDNA libraries were screened that were constructed from pooled BM stroma or mononuclear cells with an NK-1 cDNA probe. A partial clone (clone 1) was retrieved that was 97% homologous to the ED-A region of fibronectin (FN). Furthermore, sequence analyses indicated that clone 1 shared significant homology with exon 5 of NK-1. Immunoprecipitation and Western blot analysis indicated co-migration of SP and FN in 27 of 31 patients with BM fibrosis. Computer-assisted molecular modeling suggested that similar secondary structural features between FN and NK-1 and the relative electrostatic charge might explain a complex formed between FN (negative) and SP (positive). This study suggests that SP may be implicated in the pathophysiology of myelofibrosis, though its role would have to be substantiated in future research. (Blood. 2001;97:3025-3031)
Adult↗
Collagen-ligand interaction in dentinal adhesion: computer visualization and analysis.
The objective of this study was to characterize the interactions of selected ligand molecules with collagen structure through computer visualization of the reacting molecules and the resulting complexes. Five ligand molecules were studied. They were 2-Hydroxyethyl methacrylate, Glutaraldehyde-HEMA adduct, Glyceryl dimethacrylate, Methacryloyloxyethyl maleate and Acryloyloxyethyl citraconate. These ligands were selected with oxygen as a common heteroatom for a reactive or functional site. Energy minimized 3-D structures of the molecules were generated by Sybyl molecular modeling software. The structures were subjected to a systematic conformational search, yielding conformations of the molecules with a common recognition site with both steric and electrostatic complementarity to appropriate receptor sites in a type I collagen molecular structure. The ligands were also docked to collagen receptor by autodock procedures and the receptor sites where docking occurred were evaluated. The energy of the molecules and their complexes with collagen was evaluated and compared. The computer visualization results reveal that steric complementarity between receptor sites in collagen and optimally configured ligands may be the basis of micromechanical bonding between collagen and the ligands. Typically, ligands docked on the cavities of collagen molecular surface and wrapped around the cavities which follow the helical turns of the collagen macromolecule. In addition, analysis of electrostatic potential features revealed electrostatic complementarity as an additional source of interaction. Hydrogen bonds between ligands and collagen molecule were detected in the complexes of several of the conformations of all the ligands. Thus computer simulation studies show that steric and electrostatic complementarity and consequent interactions form the potential basis of binding between dentin adhesive ligands and type I collagen.
Adhesiveness↗
Three dimensional atomic model and experimental validation for the ATP-Regulated Module (ARM) of the atrial natriuretic factor receptor guanylate cyclase.
Atrial natriuretic factor (ANF) receptor guanylate cyclase (ANF-RGC) is a single chain transmembrane-spanning protein, containing both ANF binding and catalytic activities. ANF binding to the extracellular receptor domain activates the cytosolic catalytic domain, generating the second messenger cyclic GMP. Obligatory in this activation process is an intervening transduction step, which is regulated by the binding of ATP to the cyclase. The partial structural motif of the ATP binding domain of the cyclase has been elucidated and has been termed ATP Regulatory Module (ARM). The crystal structures of the tyrosine kinase domains of the human insulin receptor and haematopoietic cell kinase were used to derive a homology-based model of the ARM domain of ANF-RGC. The model identifies the precise configuration of the ATP-binding pocket in the ARM domain, accurately represents its ATP-dependent features, and shows that the ATP-dependent transduction phenomenon is a two-step mechanism. In the first step, ATP binds to its pocket and changes its configuration; in the second step, via an unknown protein kinase, it phosphorylates the cyclase for its full activation.
Adenosine Triphosphate↗
Pedicled transfer of vascularized scapular bone graft to the humerus.
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Adult↗
Allosteric regulatory step and configuration of the ATP-binding pocket in atrial natriuretic factor receptor guanylate cyclase transduction mechanism.
The atrial natriuretic factor (ANF) signal transduction mechanism consists of the transformation of the signal information into the production of cyclic GMP. The binding of ANF to its receptor, which is also a guanylate cyclase, generates the signal. This cyclase has been termed atrial natriuretic factor receptor guanylate cyclase, ANF-RGC. ANF-RGC is a single transmembrane-spanning protein. The ANF receptor domain resides in the extracellular region of the protein, and the catalytic domain is located in the intracellular region at the C-terminus of the protein. Thus, the signal is relayed progressively from the receptor domain to the catalytic domain, where it is converted into the formation of cyclic GMP. The first transduction step is the direct binding of ATP with ANF-RGC. This causes allosteric regulation of the enzyme and primes it for the activation of its catalytic moiety. The partial structural motif of the ATP binding domain in ANF-RGC has been elucidated, and it has been named ATP regulatory module (ARM). In this presentation, we provide a brief review of the ATP-regulated transduction mechanism and the ARM model. The model depicts a configuration of the ATP-binding pocket that has been experimentally validated, and the model shows that the ATP-dependent transduction process is a two- (or more) step event. The first step involves the binding of ATP with its ARM. This partially activates the cyclase and prepares it for the subsequent steps, which are consistent with its being phosphorylated and attaining the fully activated state.
Adenosine Triphosphate↗
A mutant of Sindbis virus that is resistant to pyrazofurin encodes an altered RNA polymerase.
Pyrazofurin (PZF), a cytidine analog and an inhibitor of orotate monophosphate decarboxylase, has been shown to decrease the levels of UTP and CTP in treated cells. When Sindbis virus (SV)-infected Aedes albopictus cells were treated with PZF, the yield of virus was reduced 100- to 1000-fold. By serial passage of our standard SV(STD) in Ae. albopictus cells in the presence of increasing concentrations of PZF, a mutant, SV(PZF), was derived, which was not inhibited by PZF. SV(PZF) is also resistant to adenosine, guanosine, and phosphono-acetyl-N-aspartate, all of which have been shown to decrease levels of UTP and CTP. Analysis of chimeric viruses containing sequences from the SV(PZF) and parental genomes showed that the sequence between nt 5262 and 7999 conferred the PZF-resistant phenotype. Sequencing of this region identified four mutations (nt 5750, 6627, 7543, and 7593), which are predicted to lead to amino acid changes: opal550L in nsP3 and M287L, K592I, and P609T in nsP4. Characterization of viruses containing one or more of these mutations demonstrated that all three mutations in the nsP4 coding region are required to produce full resistance to PZF. Using a molecular model of nsP4 based on the structure of HIV reverse transcriptase, we located amino acid change M287L at the tip of the fingers domain and K592I and P609T at the base of the thumb domain of the viral RNA polymerase. We suggest that these three amino acid changes in nsP4 alter the geometry of the NTP binding pocket so as to increase the affinity of the enzyme for CTP and UTP.
Adenosine↗
A plea to search for deletion polymorphism through genome scans in populations.
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Chromosome Mapping↗
Three dimensional atomic model and experimental validation for the ATP-Regulated Module (ARM) of the atrial natriuretic factor receptor guanylate cyclase.
Atrial natriuretic factor (ANF) receptor guanylate cyclase (ANF-RGC) is a single chain transmembrane-spanning protein, containing both ANF binding and catalytic activities. ANF binding to the extracellular receptor domain activates the cytosolic catalytic domain, generating the second messenger cyclic GMP. Obligatory in this activation process is an intervening transduction step, which is regulated by the binding of ATP to the cyclase. The partial structural motif of the ATP binding domain of the cyclase has been elucidated and has been termed ATP Regulatory Module (ARM). The crystal structures of the tyrosine kinase domains of the human insulin receptor and haematopoietic cell kinase were used to derive a homology-based model of the ARM domain of ANF-RGC. The model identifies the precise configuration of the ATP-binding pocket in the ARM domain, accurately represents its ATP-dependent features, and shows that the ATP-dependent transduction phenomenon is a two-step mechanism. In the first step, ATP binds to its pocket and changes its configuration; in the second step, via an unknown protein kinase, it phosphorylates the cyclase for its full activation.
Adenosine Triphosphate↗
Free oxygen radicals in acute renal failure.
OBJECTIVE: To assess the levels of free oxygen radicals in acute renal failure and their predictive value in clinical outcome. DESIGN: Prospective. SETTING: Intensive care unit. METHODS: Study was conducted in 50 children (25 with acute renal failure and 25 age and sex matched controls). Blood urea, serum creatinine, serum protein, uric acid and free oxygen radical markers were estimated in both groups. Superoxide dismutase (SOD), glutathione peroxidase(GPx) and lipid peroxide (LPO) were estimated in blood by standard techniques. RESULTS: Hemolytic uremic syndrome (HUS) was a major cause of acute renal failure (52%), rest were due to acute glomerulonephritis (AGN), septicemia and renal venous thrombosis. In the renal failure group 56% of the patients were dialyzed (peritoneal) and the mortality was 28% (7/25). The levels of SOD, GPx and LPO were significantly raised in renal failure group. Higher values of LPO, SOD and GPx were documented in subjects who expired. The most important independent variable for predicting clinical outcome was LPO with a sensitivity of 89.4%, specificity of 93%, positive predictive value of 95%. CONCLUSION: Levels of free oxygen radicals (SOD, LPO and GPx) are raised in acute renal failure and these enzymes can be used as marker of renal injury. LPO levels are highly sensitivity and specific for predicting the clinical outcome
Acute Kidney Injury↗