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Biomedical subjects

M K Shukla

Publications and source records attributed to M K Shukla.

At least 19 recordsLinked to original sources
PubMed2026

Alleviation of CO2-Induced Reductions in Tomato Photosynthesis Under Deficit Irrigation by Purple Nonsulfur Photosynthetic Bacteria.

The stimulatory effect of elevated CO2 (eCO2) on photosynthesis in most C3 crops under water deficit often declines over time due to photosynthetic acclimation. An exception occurs in plants inoculated with symbiotic nitrogen-fixing bacteria. Photosynthetic bacteria (PSB), specifically anoxygenic purple nonsulfur bacteria (Rhodopseudomonas palustris in this study), a group of nitrogen-fixing bacteria, are effective in enhancing crop photosynthesis. Therefore, this study investigated the synergistic effects of PSB and eCO2 in alleviating the effects of deficit irrigation and enhancing photosynthetic capacity in tomato plants during prolonged exposure. Our results showed that photosynthetic efficiency was significantly reduced in noninoculated plants under eCO2, and this reduction was more pronounced under water deficit. Proteomic analysis revealed that in eCO2-treated plants, the downregulation of cell wall proteins increased mesophyll resistance to CO2 diffusion, while the suppression of the photosynthetic apparatus impaired electron transport capacity, ultimately reducing CO2 assimilation efficiency. In contrast, these negative effects were alleviated by PSB inoculation. PSB promoted the upregulation of proteins involved in photosynthesis under deficit irrigation, as well as proteins related to chlorophyll biosynthesis, components of photosystem I and II, and light-harvesting complex proteins. These proteins contributed to improved photosynthetic efficiency during deficit irrigation and photosynthetic acclimation. Physiological analyses further confirmed that PSB inoculation enhanced nitrogen content, electron transport capacity, chlorophyll biosynthesis, and overall photosynthetic performance under eCO2 and deficit irrigation, resulting in improved plant growth. These findings suggest that PSB inoculation is a promising strategy to sustain and enhance the CO2 fertilization effect on crop productivity under water-limited conditions.

Photosynthesis↗
PubMed2006

Growth performance and biochemical responses of three rice (Oryza sativa L.) cultivars grown in fly-ash amended soil.

The disposal of fly-ash (FA) from coal-fired power stations causes significant economic and environmental problems. Use of such contaminated sites for crop production and use of contaminated water for irrigation not only decreases crop productivity but also poses health hazards to humans due to accumulation of toxic metals in edible grains. In the present investigation, three rice cultivars viz., Saryu-52, Sabha-5204, and Pant-4 were grown in garden soil (GS, control) and various amendments (10%, 25%, 50%, 75% and 100%) of FA for a period of 90 days and effect on growth and productivity of plant was evaluated vis-a-vis metal accumulation in the plants. The toxicity of FA at higher concentration (50%) was reflected by the reduction in photosynthetic pigments, protein and growth parameters viz., plant height, root biomass, number of tillers, grain and straw weight. However, at lower concentrations (10-25%), FA enhanced growth of the plants as evident by the increase of studied growth parameters. The cysteine and non-protein thiol (NP-SH) content showed increase in their levels up to 100% FA as compared to control, however, maximum content was found at 25% FA in Saryu-52 and Pant-4 and at 50% FA in Sabha-5204. Accumulation of Fe, Si, Cu, Zn, Mn, Ni, Cd and As was investigated in roots, leaves and seeds of the plants. Fe accumulation was maximum in all the parts of plant followed by Si and both showed more translocation to leaves while Mn, Zn, Cu, Ni and Cd showed lower accumulation and most of the metal was confined to roots in all the three cultivars. As was accumulated only in leaves and was not found to be in detectable levels in roots and seeds. The metal accumulation order in three rice cultivars was Fe > Si > Mn > Zn > Ni > Cu > Cd > As in all the plant parts. The results showed that rice varieties Saryu-52 and Sabha-5204 were more tolerant and could show improved growth and yield in lower FA application doses as compared to Pant-4. Thus, Sabha-5204 and Saryu-52 are found suitable for cultivation in FA amended agricultural soils for better crop yields.

Biomass↗
PubMed2006

Theoretical study of interaction of urate with li(+), na(+), k(+), be(2+), mg(2+), and ca(2+) metal cations.

The geometries and energetics of complexes of Li(+), Na(+), K(+), Be(2+), Mg(2+), and Ca(2+)metal cations with different possible uric acid anions (urate) were studied. The complexes were optimized at the B3LYP level and the 6-311++G(d,p) basis set. Complexes of urate with Mg(2+), and Ca(2+)metal cations were also optimized at the MP2/6-31+G(d) level. Single point energy calculations were performed at the MP2/6-311++G(d,p) level. The interactions of the metal cations at different nucleophilic sites of various possible urate were considered. It was revealed that metal cations would interact with urate in a bi-coordinate manner. In the gas phase, the most preferred position for the interaction of Li(+), Na(+), and K(+) cations is between the N(3) and O(2) sites, while all divalent cations Be(2+), Mg(2+), and Ca(2+) prefer binding between the N(7) and O(6) sites of the corresponding urate. The influence of aqueous solvent on the relative stability of different complexes has been examined using the Tomasi's polarized continuum model. The basis set superposition error (BSSE) corrected interaction energy was also computed for complexes. The AIM theory has been applied to analyze the properties of the bond critical points (electron densities and their Laplacians) involved in the coordination between urate and the metal cations. It was revealed that aqueous solvation would have significant effect on the relative stability of complexes obtained by the interaction of urate with Mg(2+) and Ca(2+)cations. Consequently, several complexes were found to exist in the water solution. The effect of metal cations on different NH and CO stretching vibrational modes of uric acid has also been discussed.

Algorithms↗
PubMed2006

Effect of Bradykinin on Murrah buffalo (Bubalus bubalis) semen cryopreservation.

Keeping in view the poor freezability of bubaline semen in conventionally used extenders, this study was conducted on three Murrah bulls to improve semen cryopreservation with the incorporation of Bradykinin (0.5, 1.0 and 2.0 ng ml(-1)) in routinely used egg yolk tris-glycerol (EYTG) extender. Bradykinin (2.0 ng ml(-1)) had significant (P<0.05) beneficial effect on live sperm % (81.6+/-1.8) and hypo osmotic swelling (HOS) % (63.0+/-1.3) as compared to their respective control values of 73.4+/-2.1 and 56.3+/-2.0 at 0 h post freezing. The post-thaw progressive sperm motility in semen samples diluted with EYTG containing 2.0 ng ml(-1) Bradykinin (65.5+/-1.4) was also significantly (P<0.01) higher than control (60.3+/-1.9) at 0 h post freezing. Thus incorporation of 2 ng ml(-1) Bradykinin in buffalo semen diluted in EYTG extender may be useful in improving the quality of cryopreserved bubaline semen.

Animals↗
PubMed2005

Effect of hydration on the lowest singlet PiPi* excited-state geometry of guanine: a theoretical study.

An ab-initio computational study was performed to investigate the effect of explicit hydration on the ground and lowest singlet PiPi* excited-state geometry and on the selected stretching vibrational frequencies corresponding to the different NH sites of the guanine acting as hydrogen-bond donors. The studied systems consisted of guanine interacting with one, three, five, six, and seven water molecules. Ground-state geometries were optimized at the HF level, while excited-state geometries were optimized at the CIS level. The 6-311G(d,p) basis set was used in all calculations. The nature of potential energy surfaces was ascertained via the harmonic vibrational frequency analysis; all structures were found minima at the respective potential energy surfaces. The changes in the geometry and the stretching vibrational frequencies of hydrogen-bond-donating sites of the guanine in the ground and excited state consequent to the hydration are discussed. It was found that the first solvation shell of the guanine can accommodate up to six water molecules. The addition of the another water molecule distorts the hydrogen-bonding network by displacing other neighboring water molecules away from the guanine plane.

Guanine↗
PubMed2005

Excited state proton transfer in guanine in the gas phase and in water solution: a theoretical study.

Theoretical investigations were performed to study the phenomena of ground and electronic excited state proton transfer in the isolated and monohydrated forms of guanine. Ground and transition state geometries were optimized at both the B3LYP/6-311++G(d,p) and HF/6-311G(d,p) levels. The geometries of tautomers including those of transition states corresponding to the proton transfer from the keto to the enol form of guanine were also optimized in the lowest singlet pipi* excited state using the configuration interaction singles (CIS) method and the 6-311G(d,p) basis set. The time-dependent density function theory method augmented with the B3LYP functional (TD-B3LYP) and the 6-311++G(d,p) basis set was used to compute vertical transition energies using the B3LYP/6-311++G(d,p) geometries. The TD-B3LYP/6-311++G(d,p) calculations were also performed using the CIS/6-311G(d,p) geometries to predict the adiabatic transition energies of different tautomers and the excited state proton transfer barrier heights of guanine tautomerization. The effect of the bulk aqueous environment was considered using the polarizable continuum model (PCM). The harmonic vibrational frequency calculations were performed to ascertain the nature of potential energy surfaces. The excited state geometries including that of transition states were found to be largely nonplanar. The nonplanar fragment was mostly localized in the six-membered ring. Geometries of the hydrated transition states in the ground and lowest singlet pipi* excited states were found to be zwitterionic in which the water molecule is in the form of hydronium cation (H3O(+)) and guanine is in the anionic form, except for the N9H form in the excited state where water molecule is in the hydroxyl anionic form (OH(-)) and the guanine is in the cationic form. It was found that proton transfer is characterized by a high barrier height both in the gas phase and in the bulk water solution. The explicit inclusion of a water molecule in the proton transfer reaction path reduces the barrier height drastically. The excited state barrier height was generally found to be increased as compared to that in the ground state. On the basis of the current theoretical calculation it appears that the singlet electronic excitation of guanine may not facilitate the excited state proton transfer corresponding to the tautomerization of the keto to the enol form.

Gases↗
PubMed2004

TDDFT investigation on nucleic acid bases: comparison with experiments and standard approach.

A comprehensive theoretical study of electronic transitions of canonical nucleic acid bases, namely guanine, adenine, cytosine, uracil, and thymine, was performed. Ground state geometries were optimized at the MP2/6-311G(d,p) level. The nature of respective potential energy surfaces was determined using the harmonic vibrational frequency analysis. The MP2 optimized geometries were used to compute electronic vertical singlet transition energies at the time-dependent density functional theory (TDDFT) level using the B3LYP functional. The 6-311++G(d,p), 6-311(2+,2+)G(d,p), 6-311(3+,3+)G(df,pd), and 6-311(5+,5+)G(df,pd) basis sets were used for the transition energy calculations. Computed transition energies were found in good agreement with the corresponding experimental data. However, in higher transitions, the Rydberg contaminations were also obtained. The existence of pisigma* type Rydberg transition was found near the lowest singlet pipi* state of all bases, which may be responsible for the ultrafast deactivation process in nucleic acid bases.

Adenine↗
PubMed2000

Electronic spectra of adenine and 2-aminopurine: an ab initio study of energy level diagrams of different tautomers in gas phase and aqueous solution.

Ground and lowest two singlet excited state geometries of four tautomeric forms (N9H, N7H, N3H and N1H) of each of adenine and 2-aminopurine (2AP) were optimized using an ab initio approach employing a mixed basis set (6-311 + G* on the nitrogen atom of the amino group and 4-31G basis set on the other atoms). Excited states were generated employing configuration interaction involving single electron excitations (CIS). Subsequently, the different species were solvated in water employing the self-consistent reaction field (SCRF) approach along with the corresponding gas phase optimized geometries. Thus the observed absorption and fluorescence spectra of adenine and 2AP have been explained successfully. It is concluded that both the N9H and N7H forms of 2AP would contribute to absorption and fluorescence spectra. Further, the fluorescence of 2AP would be absorbed by its cation in which both the N9 and N7 atoms are protonated, the fluorescence of which can have an anti-Stokes component. Among the different tautomers of adenine, the N9H form would be present dominantly in the ground state in aqueous solutions but the N7H form would be produced by energy transfer and subsequent fluorescence. The N3H form of adenine appears to be responsible for the observed absorption near 300 nm by its solutions intermittently exposed to ultraviolet radiation. The rings of the different species related to 2AP and adenine remain almost planar in the pi-pi* and n-pi* singlet excited states as in the ground state. The pyramidal character of the amino group is usually less in the pi-pi* excited states than that in the corresponding ground or n-pi* excited states. Molecular electrostatic potential (MEP) maps of the molecules provide useful clues regarding phototautomerism.

2-Aminopurine↗
PubMed1999

A geometry optimization and molecular electrostatic potential mapping study of structure-activity relationship for some anti-Alzheimer agents.

Molecular geometries of some substituted (pyrroloamino)pyridines which possess anti-Alzheimer activity were optimized and potential-derived CHelpG point charges were computed using ab initio SCF molecular orbital approach employing the 3-21G basis set. AM1 molecular orbital calculations were performed using these optimized geometries and thus optimized Hybridization. Displacement Charges (HDC) combined with Löwdin charges continuously distributed in three dimension were obtained. Molecular electrostatic potential (MEP) maps of the molecules were obtained in two ways: (i) using the HDC-based model with the help of which MEP minima near the molecules were located, and (ii) using the CHelpG point charges, MEP values on the van der Waals surfaces of the molecules were computed. The MEP maps computed using both the methods have negative MEP regions near the pyridine nitrogen atom which appears to be the main binding site of the molecules with the appropriate receptor. Both electrostatic interaction and lipophilic association between these molecules and the receptor appear to contribute to biological activity.

Alzheimer Disease↗
PubMed1995

Therapeutic potential of meso 2,3-dimercaptosuccinic acid or 2,3-dimercaptopropane 1-sulfonate in chronic arsenic intoxication in rats.

The therapeutic efficacy of two thiol chelators, meso 2,3-dimercaptosuccinic acid (DMSA) or 2,3-dimercaptopropane sulfonate (DMPS) in treating chronic arsenic intoxication was investigated in male rats. Both the chelators were effective in promoting urinary arsenic excretion and restoring arsenic induced inhibition of blood delta-aminolevulinic acid dehydratase activity and hepatic glutathione level. Elevation of urinary delta-aminolevulinic acid excretion and arsenic concentration in blood, liver and kidneys were reduced significantly by both the chelators. Histopathological lesions induced by arsenic were also effectively reduced by the above chelators. DMSA being more effective than DMPS. The results suggest DMSA and DMPS to be effective antidotes for treating chronic arsenic toxicity in experimental animals.

Animals↗
PubMed1990

Plasma prolactin as an indicator of disease progression in advanced breast cancer.

Serial plasma prolactin levels were measured in 144 breast cancer patients (premenopausal [PR-M], N = 64; postmenopausal [PO-M], N = 80) and compared with respective controls. Patients with breast cancer were grouped into those who (1) developed distant metastasis, (2) developed local recurrence, (3) stable disease, and (4) responded to the various therapeutic modalities at the end of 2 years. The authors' analysis showed excellent correlation between serial plasma prolactin changes and the response to therapy or progression of disease in patients with advanced breast carcinoma.

Biomarkers, Tumor↗
PubMed1988

Prognostic value of squamous cell carcinoma antigen in patients with uterine cervical carcinoma.

Squamous cell carcinoma antigen (SCC Ag) was estimated in 30 controls, in 16 patients with benign lesions of the uterine cervix, and in 51 patients with uterine cervical carcinoma. The rate of positivity of the antigen among the cancer patients was 87% (N = 49). SCC Ag estimations were of no diagnostic value, since 37% of patients with benign lesions had elevated levels compared to controls. SCC Ag was highly correlated to histologic subtype. The highest values were obtained in keratinizing tumors, followed by large cell nonkeratinizing and small cell nonkeratinizing types. Moreover, elevation of SCC Ag was statistically significant (p less than 0.001) among all the three histologic subtypes compared to controls. However, SCC Ag levels were not consistently correlated to the stage of the disease. Patients with pretherapeutic SCC Ag levels above 30 ng/ml had a faster recurrence rate and shorter survival than those who exhibited antigen values below 2.0 ng/ml. From our results, it is suggested that SCC Ag has limited use as a parameter for early diagnosis of cervical carcinoma, but it seems to reflect advancement of the disease. These findings indicate that SCC Ag elevation may prove to be a valuable marker in predicting subclinical disease.

Antigens, Neoplasm↗
PubMed1987

Prognosis in breast carcinoma utilizing plasma carcinoembryonic antigen and histologic characteristics of the primary tumor.

Plasma carcinoembryonic antigen (CEA) concentrations in 128 patients with breast cancer were measured preoperatively. The data were related to the histologic features of the primary breast carcinoma and to the clinical follow-up data. Analysis of the plasma CEA values did not show a significant correlation with the histologic type and the histologic and nuclear grade of the primary tumor (n = 73) as well as to the presence or absence of keratin, necrosis, desmoplasia, tubule formation and mucin production. Furthermore, the results indicated that high CEA values (more than 10 ng/ml) may be associated with distant metastasis and not with the metastatic spread to lymph nodes. High CEA levels were also associated with reduced survival of the patients. This study confirms our previous report suggesting that high CEA levels are correlated with tumors of endodermal origin, whereas the CEA levels were within the normal range in the tumors of ectodermal origin. In agreement with other studies, however, it was found that the predictive value of plasma CEA concentrations in general is weak, so that the use of CEA measurement for prognosis is of limited value.

Breast Neoplasms↗