Search PubMed⌕ Search

Biomedical subjects

V Jain

Publications and source records attributed to V Jain.

At least 127 records · Page 7Linked to original sources
PubMed1994

A simple in vitro method to detect singlet oxygen and to compare photodynamic activity using alkaline phosphatase.

A simple, sensitive and reliable in vitro method based on photodynamic inactivation of alkaline phosphatase to detect singlet oxygen and for evaluating relative photosensitizing efficiencies of photosensitizers such as hematoporphyrin (Hp) and phthalocyanines has been developed and compared with photobleaching of p-nitroso dimethyl aniline (RNO) and photooxidation of L-tryptophan. Inactivation of alkaline phosphatase is dependent both on light fluence and sensitizer concentration. Scavengers like mannitol and azide anion indicated the involvement of singlet oxygen in the deactivation of alkaline phosphatase, since azide anion provided concentration dependent protection whereas mannitol had no effect and that compared to ordinary water, photoinactivation of alkaline phosphatase was three times higher in 65% D2O. Alkaline phosphatase appears to be resistant to free radical attack (particularly to OH radicals) since hydrogen peroxide alone or in presence of ferrous ions did not reduce the enzyme activity and mannitol or azide anion gave no significant protection when alkaline phosphatase was irradiated with Co-60 gamma rays up to 2 K Gy. With the present method using red light, the chloroaluminium phthalocyanine sulphonates prepared by sulphonation showed higher and the corresponding condensation product lower photodynamic activity; Hp being intermediate and Mn- and Gd-phthalocyanines had no photodynamic activity.

Alkaline Phosphatase↗
PubMed1994

Modulation of repair and fixation of UV-induced damage and its effects on mutagenesis in yeast.

Modulation of repair of UVC-induced damage under different post-irradiation nutritional conditions and its effects on mutagenesis were studied in stationary phase cells of diploid strain D7 of Saccharomyces cerevisiae. Reverse mutation and gene conversion frequencies at ILV and TRP locus were measured in the respective omission media. It was observed that post-irradiation (150 x 10(-3) J/m2) repair in presence of (i) 2-deoxy-D-glucose (2-DG, 10 mM) resulted in decreased surviving fraction (56 +/- 5%) and increase in frequencies of revertants and gene convertants (122 +/- 10% & 132 +/- 14% respectively), (ii) yeast extract enhanced the frequency of revertants to a large extent (204 +/- 18%) and (iii) yeast extract and 2-DG together further increased the frequencies of revertants (304 +/- 15%) and gene convertants (151 +/- 12%); when compared with irradiated controls in phosphate buffer glucose; the observed changes being statistically significant (P < 0.05, Student's t test). These results indicate that (i) 2DG reduces the error-free DNA repair in yeast, (ii) yeast extract increases error-prone DNA repair and thus, in combination with 2-DG, further promotes mutagenesis.

DNA Damage↗
PubMed1994

Heterogeneity in DNA content & proliferative status of human brain tumours.

Intra-tumour and inter-tumour heterogeneity in the cytokinetic organization was studied in 235 primary human brain tumours. DNA index (DI; relative tumour cell DNA content) and proliferating fraction (%PF; a measure of proliferative status) were analyzed in tumour biopsy by flow cytometry using a DNA specific fluorochrome (DAPI) and internal standards (chicken erythrocytes, CE). Incidence of micronuclei was studied in tumour biopsy tissue as well as in explants maintained in organ culture. Clonal diversity (implied by the presence of multiple peaks in the DNA histograms) was highest among medulloblastomas (44%) followed by gliomas (19%) and meningiomas (14%). Nearly 85 per cent of the malignant gliomas analyzed (histological grade III/IV) exhibited a great deal of regional variation in the proliferative status as well as micronuclei frequency as compared to meningiomas. Inter-tumoural variations in the DNA content was highest among gliomas (0.9 < DI < 3.6) and lowest among schwannomas (1.7 < DI < 2.2). Similarly, the distribution of %PF values was also broader (10-49%) in gliomas as compared to the other primary brain tumours (5-36%). Analysis of tumours taking both DI and %PF values improved the ability to discern histologically graded low and high tumours. Analysis of clonal diversity and spatial heterogeneity in the cytokinetic parameters could complement the clinicopathological findings in assessing the biological behaviour of human brain tumours, facilitating the prognostification and design of otpimal treatment regimen.

Brain Neoplasms↗
PubMed1994

Effects of 2-deoxy-D-glucose on the photosensitisation-induced bioenergetic changes in Saccharomyces cerevisiae as observed by in vivo NMR spectroscopy.

Haematoporphyrin (HP), a photosensitiser used for photodynamic therapy (PDT) of tumours, has been observed to affect the cellular energy metabolism both in the absence and presence of light. The effects of HP alone and in combination with 2-deoxy-D-glucose (2-DG) on photosensitisation-induced bioenergetic changes in yeast (Saccharomyces cerevisiae) were monitored and compared using in vivo NMR spectroscopy. Presence of HP was seen to reduce polyphosphates and inorganic phosphate in the dark. Upon photo-irradiation, polyphosphates and sugar phosphates decrease drastically with concomitant rise in inorganic phosphates. Presence of 2-DG in the medium also induced a decrease in polyphosphates and nucleotide triphosphates and the build-up of 2-deoxy-D-glucose-6-phosphate (2-DG-6-P) was clearly detectable. The combination of 2-DG and HP followed by photo-irradiation, however, induced a significant reduction in intracellular pH and beta phosphate of ATP/inorganic phosphate (beta-ATP/Pi) ratio decreased to a larger extent as compared to similar treatment without 2-DG. These observations confirm that polyphosphates are utilised as phosphogen, as phosphate store to be used during phosphate deprivation and as alternative energy source under conditions of energy deficiency induced by HP-PDT and/or 2-DG. The present results further suggest that photodynamic therapy could be made more effective in conjunction with 2-DG administration.

Deoxyglucose↗
PubMed1993

Mode of delivery in deep transverse arrest.

OBJECTIVES: To determine the trends in the mode of delivery in deep transverse arrest (DTA) over two decades and their impact on maternal morbidity and neonatal outcome. METHODS: Obstetric and neonatal records of women with DTA who delivered at Nehru Hospital, PGIMER, Chandigarh in the years 1970, 1980 and 1990 were analyzed. RESULTS: Although Kielland's forceps was used very frequently in 1970 (44.4%) it had disappeared by 1990 because of increased morbidity associated with it. Instead, use of vacuum extractor and cesarean section has increased over the years. Manual rotation forceps extraction was the most commonly used vaginal method of delivery over two decades (49.5%). Perinatal outcome was better with manual rotation forceps extraction or vacuum extraction as compared to Kielland's forceps. Cesarean section was associated with a high incidence of birth asphyxia (30%). CONCLUSIONS: Manual rotation forceps extraction and vacuum extraction are safe methods of delivery in DTA. Cesarean section as an alternative does not improve the perinatal outcome.

Cesarean Section↗
PubMed1993

Modification of radiation damage in transformed mammalian cells by 5-bromo-2-deoxy-uridine and 2-deoxy-D-glucose.

The effects of 2-deoxy-D-glucose (2-DG) and 5-bromo-2-deoxy-uridine (BrdU) on gamma ray (60Co) induced damage were studied in monolayer cultures of transformed mammalian (BHK-21) cells. Micronuclei formation and changes in DNA content dispersion were used as indices of cytogenetic damage. Exposure of cells to BrdU (0.8 microM) for nearly two cell cycles before irradiation significantly increased micronuclei formation in exponentially growing cells. Incubation of irradiated cells under suboptimal growth conditions (in HBSS) for 4 hr, instead of growth medium, decreased the manifestation of damage. However, post-irradiation presence of 2-DG (5 mM, equimolar with glucose; 4 hr) in growth medium or HBSS significantly increased radiation damage. The effects of 2-DG treatment following irradiation in plateau phase were quantitatively less. These results suggest that: (i) radiation induced DNA lesions leading to micronuclei formation in BrdU incorporated cells are partly repairable; (ii) 2-DG could increase radiation induced cytogenetic damage in transformed mammalian cells, possibly by inhibiting the cellular repair processes; and (iii) combination of 2-DG treatment may decrease the BrdU doses required for radiosensitization of proliferating tumour cell populations.

Animals↗