Biomedical subjects

J Srivastava

Publications and source records attributed to J Srivastava.

5 recordsLinked to original sources

PubMed2006

Mineral profile and variability in vegetable amaranth (Amaranthus tricolor).

Populations in North India depend on a number of vegetable crops of which Amaranthus spp. is the most important since it is the only crop available in the hot summer months when no other foliage crop grows in the field. However, reports on mineral composition of leaves are rare with absolutely no information on the qualitative improvement of foliage yield with special reference to minerals. Studies on correlation among the minerals as well as with yield and leaf attributes are also lacking. Hence, we report the proximate mineral composition in 30 strains of A. tricolor along with some suggestions for qualitative improvement of the foliage yield with reference to minerals. Our study showed that vegetable amaranth is a rich source of minerals like calcium (1.7 +/- 0.04 g/100 g), iron (1233.8 +/- 50.02 mg/kg), and zinc (791.7 +/- 28.98 mg/kg). The heritability estimates were high for most of the traits, with potassium and calcium showing high values, while comparatively lower values were recorded for magnesium and nickel. Nickel was the only mineral that showed positive correlation with all the minerals, as well as with leaf size and foliage yield. Zinc showed strong positive relationship with iron (0.66**) and manganese (0.74**), and was the only mineral exhibiting significant positive association with foliage yield. This study would be of use in enhancement of selected minerals in different regions according to local preferences and nutrient deficiency prevalent among the populations.

Amaranthus↗

PubMed2005

Src-dependent ezrin phosphorylation in adhesion-mediated signaling.

In addition to providing a regulated linkage between the membrane and the actin cytoskeleton, ezrin participates in signal transduction pathways. Here we describe that expression of the ezrin Y145F mutant delays epithelial cell spreading on fibronectin by inhibiting events leading to FAK activation. The defect in spreading was rescued by the overexpression of catalytically functional Src. We demonstrate that ezrin Y145 is phosphorylated in A431 cells stimulated with epidermal growth factor (EGF) and in v-Src-transformed cells. Moreover in cells devoid of Src, SYF-/- fibroblasts, ezrin Y145 phosphorylation could only be detected upon the introduction of an active form of Src. The phosphorylation of ezrin at Y145 required prior binding of the Src SH2 domain to ezrin. Our results further show that Src activity influences its binding to ezrin and a positive feedback mechanism for Src-mediated Y145 phosphorylation is implied. Interestingly, cells expressing ezrin Y145F did not proliferate when cultured in a 3D collagen gel. Collectively, our results demonstrate a key signaling input of Src-dependent ezrin phosphorylation in adhesion-mediated events in epithelial cells.

Actins↗

PubMed2001

Mechanism of malarial haem detoxification inhibition by chloroquine.

The haem detoxification pathway of the malaria parasite Plasmodium falciparum is a potential biochemical target for drug development. Free haem, released after haemoglobin degradation, is polymerized by the parasite to form haemozoin pigment. Plasmodium falciparum histidine-rich protein-2 (Pfhrp-2) has been implicated as the catalytic scaffold for detoxification of haem in the malaria parasite. Previously we have shown that a hexapeptide repeat sequence (Ala-His-His-Ala-Ala-Asp), which appears 33 times in Pfhrp-2, may be the major haem binding site in this protein. The haem binding studies carried out by ourselves indicate that up to 18 equivalents of haem could be bound by this protein with an observed K(d) of 0.94 microM. Absorbance spectroscopy provides evidence that chloroquine is capable of extracting haem bound to Pfhrp-2. This was supported by the K(d) value, of 37 nM, observed for the haem-chloroquine complex. The native PAGE studies reveal that the formation of the haem-Pfhrp-2 complex is disrupted by chloroquine. These results indicate that chloroquine may be acting by inhibiting haem detoxification/binding to Pfhrp-2. Moreover, the higher affinity of chloroquine for haem than Pfhrp-2 suggests a possible mechanism of action for chloroquine; it may remove the haem bound to Pfhrp-2 and form a complex that is toxic to the parasite.

Amino Acid Sequence↗

PubMed1998

A molecular investigation of the obese phenotype in the Aston University strain of ob/ob mice and the Japanese Kuo Kondo mice.

The aim of this work was to determine the role of the ob gene in the obese phenotype observed in the Aston University Strain of ob/ob mouse and the Japanese Kuo Kondo (KK) mouse. After RT-PCR amplification of the ob RNA, the transcript was cloned into the vector pCR3 and three individual clones from each strain were sequenced. It was confirmed that the Aston University strain of ob/ob mice shared the same C-T mutation found in the Jackson Laboratory C57BL/6J ob/ob strain whereas the Japanese KK mice showed wild-type ob gene expression. This study indicates that the ob mutation has survived unchanged following the separation of the two strains of ob/ob mice, and secondly, that the molecular basis of the obese phenotype in the KK mice is not due to mutations in the ob gene.

Animals↗

PubMed1986

Stimulation of K+ flux into mitochondria by phenylarsine oxide.

The dithiol-reactive reagent phenylarsine oxide causes a pH-dependent stimulation of unidirectional K+ flux into respiring rat liver mitochondria. This stimulation is diminished by subsequent addition of either the dithiol 2,3-dimercaptopropanol or the monothiol 2-mercaptoethanol. In contrast, uncoupling by phenylarsine oxide is reversed by 2,3-dimercaptopropanol but not by 2-mercaptoethanol. The data suggest separate sites of interaction of phenylarsine oxide with mechanisms of K+ entry and ATP synthesis. Stimulatory effects of mersalyl and phenylarsine oxide on K+ influx are not additive. Thus PheASO and mersalyl may affect K+ influx at a common site. Pretreatment of the mitochondria with DCCD, which inhibits K+ influx, fails to alter sensitivity to PheAsO or mersalyl. Thus the DCCD binding site associated with the K+ influx mechanism appears to be separate from and independent of the sulfhydryl group(s) which mediate stimulation of K+ influx by PheAsO and mersalyl. PheAsO, like mersalyl, also increases the rate of unidirectional K+ efflux from respiring mitochondria. The combined presence of PheAsO plus mersalyl causes a greater stimulation of K+ efflux than is observed with either reagent alone.

Animals↗