Browsing by Author "P.K. Pandey"

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Asymptotic behavior of the convolution transform
(1993) R.S. Pathak; P.K. Pandey
Carmichael and Pathak [1] have given abelian theorems for the H-transform of classical functions and generalized functions as the complex variable of the transform approaches zero or infinity in a wedge domain in the right half plane. Many classical integral transforms are special cases of H-transform. The convolution transform studied by Hirschman and Widder [3] is not a special case of the H-transform. In fact Tanno [4] has shown that certain generalized convolution transform includes the H-transform as a special case. In this paper Abelian theorems for the convolution transform are obtained. In obtaining these results we follow closely Zemanian [5] and Carmichael and Pathak [1]. © 1993, Taylor & Francis Group, LLC. All rights reserved.
Copper uptake by free and immobilized cyanobacterium
(1989) S.P. Singh; S.K. Verma; R.K. Singh; P.K. Pandey
Copper uptake in free and immobilized cells of the cyanobacterium Nostoc calcicola has been examined. The immobilized cells invariably maintained a higher profile of Cu intake rate (12.7 nmol mg-1 protein min-1) over the free cells (6.0 nmol mg-1 protein min-1). The total Cu uptake in immobilized cells was almost two and a half-times more than their free cell counterpart under identical experimental conditions. Also, the immobilized cells showed a stronger positive correlation between Cu adsorption and uptake. The results have been discussed in terms of improved metabolic efficiency of immobilized cells. © 1989.
Cu uptake in a cyanobacterium: Fate of selected photochemical reactions
(Springer-Verlag, 1992) P.K. Pandey; C.B. Singh; S.P. Singh
Cu uptake in the diazotrophic cyanobacterium Nostoc calcicola Bréb. was accompanied by inhibitions in the in vivo activities of photosystem (PS) II, PS I,14CO2-fixation, and decline in the ATP pool. Cyanobacterial cells, while saturated for Cu uptake within 1 h at 40 μM Cu, showed more than 50% inhibition of PS II and 95.4% of14CO2 fixation compared with only 15.5% decrease in the PS I activity. The total extractable ATP content also declined by 32.2% within 1 h. In a subsequent follow-up study lasting 72 h, PS II activity and14CO2 fixation showed complete inhibition, in contrast to 34.4% of PS I activity and 4.2% of ATP still remaining unaffected. The results have been discussed in the light of multiple effects of Cu during and subsequent to its uptake by the cyanobacterium. © 1992 Springer-Verlag.
Cu2+ efflux and its regulation in Cu-resistant (Cu(r)) cyanobacterium Nostoc calcicola BREB.
(Wiley-VCH Verlag, 1997) P.K. Pandey; S.P. Singh; P.S. Bisen
[No abstract available]
Factors regulating copper uptake in free and immobilized cyanobacterium
(1992) S.P. Singh; R.K. Singh; P.K. Pandey; A. Pant
The effect of population size, redox potential, exogenous ATP and complexing agents on Cu uptake by free and immobilized cyanobacterium Nostoc calcicolaBréb. has been studied. Cu uptake was regulated by the population size. In such comparisons, the immobilized cells had a greater longevity. Low pH conditions enhanced Cu uptake. Exogenous ATP (10 μmol/L) supplied to dark-grown free and immobilized cells did not support Cu uptake to the extent of light-grown cells. Experiments involving natural as well as synthetic complexing agents clearly established the superiority of soil extract and spent medium over EDTA (10 μmol/L), in sequestering Cu in free as well as immobilized cells. © 1992, Folia Microbiologica. All rights reserved.
Hg2+ uptake in a cyanobacterium
(Springer-Verlag, 1993) P.K. Pandey; S.P. Singh
The uptake of Hg2+ and its regulation in the cyanobacterium Nostoc calcicola Bréb. was studied. Hg2+ uptake pattern consisted of two distinct phases: (a) rapid binding of the cation to the negatively charged cell surface (first 10 min) and (b) its subsequent metabolism-dependent intracellular import, at least up to 40 min (saturating concentration 1.5 μM Hg2+, Km=1.0μM Hg2+ and Vmax 0.21 nmol Hg2+ mg-1 protein min-1). Hg2+ influx, to a major extent, depended on photosynthetically generated energy, and the supply of exogenous ATP (10 μM) or DCMU (5 μM) suggested the vital role of PS II-mediated energy to support the process. The significant lowering in Hg2+ uptake rate as well as total cellular Hg2+ in the presence of p-chloromercuribenzoate (pCMB), azide (NaN3), N,N′-dicyclohexycarbodiimide (DCCD), and thiol (mercaptoethanol) indicated the role of membrane potential,-SH groups, and ATP hydrolysis in regulating Hg2+ transport. While Cu2+ antagonized Hg2+ intake, Ni2+ showed synergism. © 1993 Springer-Verlag New York Inc.
Tomato leaf curl Gujarat virus, a New Begomovirus Species Causing a Severe Leaf Curl Disease of Tomato in Varanasi, India
(American Phytopathological Society, 2003) S. Chakraborty; P.K. Pandey; M.K. Banerjee; G. Kalloo; C.M. Fauquet
The biological and molecular properties of Tomato leaf curl Gujarat virus from Varanasi, India (ToLCGV-[Var]) were characterized. ToLCGV-[Var] could be transmitted by grafting and through whitefly transmission in a persistent manner. The full-length genome of DNA-A and DNA-B of ToLCGV-[Var] was cloned in pUC18. Sequence analysis revealed that DNA-A (AY190290) is 2,757 bp and DNA-B (AY190291) is 2,688 bp in length. ToLCGV-[Var] could infect and cause symptoms in tomato, pepper, Nicotiana benthamiana, and N. tabacum when partial tandem dimeric constructs of DNA-A and DNA-B were co-inoculated by particle bombardment. DNA-A alone also is infectious, but symptoms were milder and took longer to develop. ToLCGV-Var virus can be transmitted through sap inoculation from infected tomato plants to the above-mentioned hosts causing the same symptoms. Open reading frames (ORFs) in both DNA-A and DNA-B are organized similarly to those in other begomoviruses. DNA-A and DNA-B share a common region of 155 bp with only 60% sequence identity. DNA-B of ToLCGV-[Var] shares overall 80% identity with DNA-B of Tomato leaf curl New Delhi virus-Severe (ToLCNDV-Svr) and 75% with ToLCNDV-[Lucknow] (ToLCNDV-[Luc]). Comparison of DNA-A sequence with different begomoviruses indicates that ToLCGV-[Var] shares 84% identity with Tomato leaf curl Karnataka virus (ToLCKV) and 66% with ToLCNDV-Svr. ToLCGV-[Var] shares a maximum of 98% identity with another isolate of the same region (ToLCGV-[MIr]; AF449999) and 97% identity with one isolate from Gujarat (ToLCGV-[Vad]; AF413671). All three viruses belong to the same species that is distinct from all the other geminivirus species described so far in the genus Begomovirus of the family Geminiviridae. The name Tomato leaf curl Gujarat virus is proposed because the first sequence was taken from an isolate of Gujarat, India.