Biomedical subjects

A Nazir

Publications and source records attributed to A Nazir.

5 recordsLinked to original sources

PubMed2004

Selective spin coupling through a single exciton.

We present a novel scheme for performing a conditional phase gate between two spin qubits in adjacent semiconductor quantum dots through delocalized single exciton states, formed through the interdot Förster interaction. We consider two resonant quantum dots, each containing a single excess conduction band electron whose spin embodies the qubit. We demonstrate that both the two-qubit gate and arbitrary single-qubit rotations may be realized to a high fidelity with current semiconductor and laser technology.

Journal Article↗

PubMed2002

Toxicity of argemone oil: effect on hsp70 expression and tissue damage in transgenic Drosophila melanogaster (hsp70-lacZ) Bg9.

The effect of argemone oil on hsp70 expression and tissue damage was investigated by studying beta-galactosidase activity, Western blotting and hybridization, and trypan blue staining in the larval tissues of transgenic Drosophila melanogaster (hsp70-lacZ)Bg9. Different concentrations of argemone oil were mixed with food and third-instar larvae were allowed to feed on them for different time intervals (2, 4, 24, and 48 h). Argemone oil was found to induce hsp70 even in the lowest concentration of the adulterant while maximum tissue damage was observed in the higher two treatment groups. Malpighian tubules and midgut tissue reflected maximum damage as evidenced by both high beta-galactosidase activity and trypan blue staining in these tissues. A prior temperature shock treatment to the larvae was enough to protect the larvae from argemone oil-induced tissue damage as evidenced by little or no trypan blue staining. The present study suggests the cytotoxic potential of argemone oil and further strengthens the evidence for the use of hsp70 as a biomarker in risk assessment.

Animals↗

PubMed2001

Effect of three chlorinated pesticides on hsromega stress gene in transgenic Drosophila melanogaster.

Expression of hsromega stress gene in the third-instar larvae of 951-lacZ2 (hsromega-lacZ having-844pb sequence) and 498-lacZ1 (hrsomega-lacZ having -498bp sequence) strains of Drosophila melanogaster at LC(50) and lower dietary concentrations of hexachlorocyclohexane (HCH) pentachlorophenol (PCP), and endosulfan was examined in relation to larval mortality by beta galactosidase activity, vital dye staining, and salivary gland polytene chromosome puffing. Our results showed that both HCH and PCP at lower concentrations evoked strong hsromega stress gene expression in the larval tissues while endosulfan did not. On the other hand, puffing data revealed that endosulfan at lower doses, induced well-developed puff at the resident site (93D) of the hsromega gene but the transgenic sites (30B in 951-lacZ2 and 44B in 498-lacZ1 strain) did not show any well-developed puff. Regression in hsromega stress gene expression in 951-lacZ2 strain at LC(50) concentrations of HCH and PCP after 48 h was concurrent with extensive tissue damage as evident by trypan blue staining. Similarly, strong hsromega expression was accompanied by insignificant trypan blue staining in the larval tissues of this strain after shorter duration of exposure (2-12 h) to these toxicants. Although endosulfan under similar experimental condition did not induce hsromega, strong trypan blue staining indicated extensive tissue damage after 48 h of exposure. The present study suggests that all the three toxicants pose cytotoxic potential to Drosophila. While protective role of this stress gene was evident at the initial stages of exposure, extensive tissue damage in the later stages of intoxication accompanied by autorepression of hsromega led to larval mortality. The study further suggests that -844bp upstream sequence of the gene is adequate for hsromega inducibility against HCH and PCP but not for endosulfan for which responsive elements may be searched further upstream.

Animals↗

PubMed2001

Chlorpyrifos-induced hsp70 expression and effect on reproductive performance in transgenic Drosophila melanogaster (hsp70-lacZ) Bg9.

Expression of hsp70 in the third-instar larval tissues of transgenic Drosophila melanogaster (hsp70-lacZ) following dietary exposure to organophosphate insecticide chlorpyrifos for various time intervals was investigated. Effect of the chemical on different developmental stages of the fly was also evaluated by looking at survivorship, hatchability, emergence, fecundity, fertility, and reproductive performance. Our results showed that the toxicant evokes profound cytotoxic effect as evidenced by dark blue staining in salivary gland, proventriculus, brain ganglia, and midgut in the lowest concentration of the chemical following 24 and 48 h of exposure. On the other hand, a significant increase (61%) in hsp70 expression in the above larval tissues was observed in the next higher concentration of the toxicant after 6 h exposure when compared with that of the lowest dose. A further increase in exposure time caused 100% larval mortality. Similarly, larvae exposed to higher concentrations of the toxicant, exhibited 100% mortality within 1 h of treatment. The insecticide caused a delay in emergence and a severe reduction in survivorship of the flies in a dose-dependent manner with 100% mortality within a day of exposure in the highest dosed group. A delay in emergence by 3 days was evident even in the lowest concentration of the chemical. A drastic effect of the chemical on hatchability was found in the highest dosed group with 100% embryonic mortality at post-16 stage of the embryo. Reproductive performance was significantly affected even in the lowest dosed group. The present study suggests that certain larval tissues of Drosophila, a nontarget organism, are vulnerable to chlorpyrifos as evidenced by hsp70 expression. Further, the adverse effect of the toxicant is reflected on various stages of development of the fly including reproductive performance.

Animals↗

PubMed2001

Internet: a major resource for toxicologists.

Use of the Internet in developing countries is now growing faster. Internet has created a new conduit not only for communication but also in the access, sharing and exchange of information among scientists. The Internet is now viewed as the world's biggest library where retrieval of scientific literature and other information resources are possible within seconds. Large volumes of toxicological information resources are available on the Internet. This review outlines some sites that may be of great importance and useful to the toxicologist.

Internet↗