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1.
A survey for malic enzyme (Me) in laboratory strains of species A and species B of Anopheles culicifacies had uncovered two electrophoretic variants, slow and fast, in two strains of species B. Genetic analysis revealed the two variants to be codominant alleles segregating at a locus, Me, which is sex linked. Because of the XX-XY sex determining mechanism, in F1 females, two electromorphs, viz., slow and fast, were observed, whereas in males only one electromorph of maternal origin was seen. Linkage experiments with another X-linked mutant, white eye (w), indicated the map distance between the two loci to be 9.52 +/- 0.86.  相似文献   
2.
Maternally inherited variants, which arose within a laboratory colony of Culex pipiens fatigans, have been studied by rearing cultures from single egg rafts. Segregation, i.e, variation of cytoplasmic incompatibility properties between the male progeny of individual females, was demonstrated. Also, from the daughters of individual females, sub-lines were derived within which all the males showed the same incompatibility or compatibility properties. Among the descendants of tetracycline-treated individuals were lines which superficially simulated these phenomena, but theses lines ultimately reverted to the cytoplasmic compatibility type of the strain which was submitted to the treatment. The types of variation s in cytoplasmic incompatibility properties that have been studied are discussed.  相似文献   
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4.
Nitric-oxide synthase (NOS) catalyzes the formation of NO and citrulline from l-arginine and oxygen. However, the NO so formed has been found to auto-inhibit the enzymatic activity significantly. We hypothesized that the NO reactivity is in part controlled by hydrogen bonding between the conserved tryptophan residue (position 409 in the neuronal isoform of NOS (nNOS)) and the cysteine residue that forms the proximal bond to the heme. By using resonance Raman spectroscopy and NO as a probe of the heme environment, we show that in the W409F and W409Y mutants of the oxygenase domain of the neuronal enzyme (nNOSox), the Fe-NO bond in the Fe3+NO complex is weaker than in the wild type enzyme, consistent with the loss of a hydrogen bond on the sulfur atom of the proximal cysteine residue. The weaker Fe-NO bond in the W409F and W409Y mutants might result in a faster rate of NO dissociation from the ferric heme in the Trp-409 mutants as compared with the wild type enzyme, which could contribute to the lower accumulation of the inhibitory NO-bound complexes observed during catalysis with the Trp-409 mutants (Adak, S., Crooks, C., Wang, Q., Crane, B. R., Tainer, J. A., Getzoff, E. D., and Stuehr, D. J. (1999) J. Biol. Chem. 274, 26907-26911). The optical and resonance Raman spectra of the Fe2+NO complexes of the Trp-409 mutants differ from those of the wild type enzyme and indicate that a significant population of a five-coordinate Fe2+NO complex is present. These data show that the hydrogen bond provided by the Trp-409 residue is necessary to maintain the thiolate coordination when NO binds to the ferrous heme. Taken together our results indicate that the heme environment on the proximal side of nNOS is critical for the formation of a stable iron-cysteine bond and for the control of the electronic properties of heme-NO complexes.  相似文献   
5.

Background

Control of Aedes aegypti, the mosquito vector of dengue, chikungunya and yellow fever, is a challenging task. Pyrethroid insecticides have emerged as a preferred choice for vector control but are threatened by the emergence of resistance. The present study reports a focus of pyrethroid resistance and presence of two kdr mutations—F1534C and a novel mutation T1520I, in Ae. aegypti from Delhi, India.

Methodology/Principal Findings

Insecticide susceptibility status of adult-female Ae. aegypti against DDT (4%), deltamethrin (0.05%) and permethrin (0.75%) was determined using WHO''s standard insecticide susceptibility kit, which revealed resistance to DDT, deltamethrin and permethrin with corrected mortalities of 35%, 72% and 76% respectively. Mosquitoes were screened for the presence of kdr mutations including those reported earlier (I1011V/M, V1016G/I, F1534C, D1794Y and S989P), which revealed the presence of F1534C and a novel mutation T1520I. Highly specific PCR-RFLP assays were developed for genotyping of these two mutations. Genotyping using allele specific PCR and new PCR-RFLP assays revealed a high frequency of F1534C (0.41–0.79) and low frequency of novel mutation T1520I (0.13). The latter was observed to be tightly linked with F1534C and possibly serve as a compensatory mutation. A positive association of F1534C mutation with DDT and deltamethrin resistance in Ae. aegypti was established. However, F1534C-kdr did not show significant protection against permethrin.

Conclusions/Significance

The Aedes aegypti population of Delhi is resistant to DDT, deltamethrin and permethrin. Two kdr mutations, F1534C and a novel mutation T1520I, were identified in this population. This is the first report of kdr mutations being present in the Indian Ae. aegypti population. Highly specific PCR-RFLP assays were developed for discrimination of alleles at both kdr loci. A positive association of F1534C mutation with DDT and deltamethrin resistance was confirmed.  相似文献   
6.
Bishydrazides are versatile linkers for attaching glycans to substrates for lectin binding and pathogen detection schemes. The α,ω-bishydrazides of carboxymethylated hexa(ethylene glycol) (4) can be conjugated at one end to unprotected oligosaccharides, then attached onto carrier proteins, tethered onto activated carboxyl-terminated surfaces, or functionalized with a photoactive cross-linking agent for lithographic patterning. Glycoconjugates of bishydrazide 4 can also be converted into dithiocarbamates (DTCs) by treatment with CS(2) under mild conditions, for attachment onto gold substrates. The immobilized glycans serve as recognition elements for cell-surface lectins and enable the detection and capture of bacterial pathogens such as Pseudomonas aeruginosa by their adsorption onto micropatterned substrates. A detection limit of 103 cfu/mL is demonstrated, using a recently introduced method based on optical pattern recognition.  相似文献   
7.
The 3 laboratory-colonized malaria vectors, i.e., Anopheles stephensi, An. sundaicus, and An. fluviatilis, were studied for their comparative susceptibility to Plasmodium vivax sporogony. There was no significant difference in oocyst and sporozoite recruitment by these 3 species, whereas the geometric mean (GM) of the oocyst number per midgut was significantly lower in An. fluviatilis as compared with that in the other 2 species. There was no difference in the GM of oocyst between An. stephensi and An. sundaicus. Adaptability to laboratory conditions and susceptibility to plasmodial infection suggest that An. fluviatilis and An. sundaicus can also be used as a vector model for vector-parasite interaction studies.  相似文献   
8.
9.
Ascorbate peroxidase from L. Major (LmAPX) is a functional hybrid between cytochrome c peroxidase (CCP) and ascorbate peroxidase (APX). We utilized point mutagenesis to investigate if a conserved proximal tryptophan residue (Trp208) among Class I peroxidase helps in controlling catalysis. The mutant W208F enzyme had no effect on both apparent dissociation constant of the enzyme-cytochrome c complex and K(m) value for cytochrome c indicating that cytochrome c binding affinity to the enzyme did not alter after mutation. Surprisingly, the mutant was 1000 times less active than the wild type in cytochrome c oxidation without affecting the second order rate constant of compound I formation. Our diode array stopped-flow spectral studies showed that the substrate unbound wild type enzyme reacts with H(2)O(2) to form compound I (compound II type spectrum), which was quite different from that of compound I in W208F mutant as well as horseradish peroxidase (HRP). The spectrum of the compound I in wild type LmAPX showed a red shift from 409 nm to 420 nm with equal intensity, which was broadly similar to those of known Trp radical. In case of compound I for W208F mutant, the peak in the Soret region was decreased in heme intensity at 409 nm and was not shifted to 420 nm suggesting this type of spectrum was similar to that of the known porphyrin pi-cation radical. In case of an enzyme-H(2)O(2)-ascorbate system, the kinetic for formation and decay of compound I and II of a mutant enzyme was almost identical to that of a wild type enzyme. Thus, the results of cytochrome c binding, compound I formation rate and activity assay suggested that Trp208 in LmAPX was essential for electron transfer from cytochrome c to heme ferryl but was not indispensable for ascorbate or guaiacol oxidation.  相似文献   
10.
The present work is emphasised with the herbicidal tolerance of Azolla pinnata R.Br. and its modulation with TiO2 nano-particle. Both carbohydrate and nitrogen metabolism were effected with 2,4-D as herbicide and in few cases TiO2-NP had recovered few detrimental effects. From the nutrient status in Azolla it recorded the recovery of nitrogen as well as potassium by TiO2-NP but not in case of phosphorus. However, a conversion of nitrate to ammonium was more induced by TiO2-NP under herbicidal toxicity. Similar results were obtained for inter-conversion of amino acid–nitrate pool, but no changes with glutamine synthase activity with TiO2-NP. Initially, the effects of 2,4-D was monitored with changes of chlorophyll content but had not been recovered with nanoparticle. Photosynthetic reserves expressed as both total and reducing sugar were insensitive to TiO2-NP interference but activity of soluble and wall bound invertase was in reverse trend as compared to control. The 2,4-D mediated changes of redox and its oxidative stress was ameliorated in plants with over expressed ADH activity. As a whole the Azolla bio system with TiO2 supplementation may be useful in sustenance against 2,4-D toxicity through recovery of nitrogen metabolism. Thus, Azolla-TiO2-NP bio system would be realised to monitor the herbicidal toxicity in soil and its possible bioremediation.  相似文献   
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